In this post I'm giving the descriptions of the multiple government types available in Scifi mode. Confederation is human-only, while The Great Joining is klackon-only. The Julian Bureaucracy wonder allows one to get around those restrictions, though.

Pandemonium
Pandemonium is not so much a type of government as the lack of any stable government. Pandemonium occurs when your civilization's government falls or when you decide to have a Revolution. After a few turns of Pandemonium, you will be able to reconstitute your government. Pandemonium is similar to Despotism, except that the inaccuracy rate is very high (see Despotism). No taxes are collected during a Pandemonium, and no scientific research is conducted.

Despotism
In a Despotism, the ruler has absolute control over his or her subjects, and this control is usually enforced by the military. This system has a tendency to minimize individual freedom, and reduce the efficiency of production efforts.

* Each unit above the city size costs one materiel per turn.
* Settler units require one Food per turn.

Up to three military units stationed in each city help maintain order, making one unhappy citizen (per unit) content.

Despotism has a high rate of inaccuracy and waste. The level of inaccuracy in a particular city is based on its distance from your capital.

* Under a Despotism, none of the tax rates (science, taxes, and entertainment) may be set higher than 60%.
* Any terrain square that ordinarily produces three or more of any resource (Food, Materiel, or Data) produces one less.
* Because of Despotism's high rate of inaccuracy, it is almost always an inferior form of government. Try to switch to something else as soon as possible.

Collective
A Collective government is ruled by a Central Committee, which in turn is overseen by the Doyen. The actions of these rulers, however, simply reflect the will of the population, as collected through tamper-proof crystal thermionic communications techniques. While the technology is reliable, the actions of those in power, once elected, are not. The automation of the infrastructure underlying much of the economy and the military make abuses of power all too easy to commit in secrecy, and often without repercussions.

* Each unit beyond the fourth unit costs one materiel per turn.
* Settler units require two Food per turn.

Up to three military units stationed in each city help maintain order, making TWO unhappy citizens (per unit) content.

In the Collective, peer review and the free flow of information virtually eliminates fraud and mistakes in data recording. Your cities, therefore, experience relatively low rates of inaccuracy.

* All Salmagundy units produced under Collective governments are Veterans.
* In the Collective, none of the tax rates (science, taxes, and entertainment) may be set higher than 80%.

* The Collective is best for large, far-flung empires that need to maintain a large military.
* Use your powerful spies to steal technology.

Proteocracy
A Proteocracy is ruled by a Chimeron--the most flexible adult citizen willing to serve. Several of the least flexible citizens are conscripted into the Senate, to offer a counterpoint to the Chimeron's policies. Proteocracy is an extremely plastic and responsive form of government, which results in great efficiency from its cities and citizens, but also higher expectations for personal freedom and happiness.

* Each unit costs one materiel per turn.
* Settler units require two Food per turn.

Each unit which is not in a friendly city or a force field within 3 spaces of a friendly city causes two citizens in its home city to become unhappy.

Proteocracies experience no inaccuracy or waste.

* There are no limits on the tax rate settings (science, taxes, and entertainment).
* Under a Proteocracy, each terrain square that ordinarily produces at least one unit of data produces an extra unit.
* The units and cities of a Proteocracy are immune to bribery.
* Your Senate may force a peaceful solution in a conflict.

* Proteocracies can produce spectacular amounts of revenue and scientific research. However, because of the severe happiness restrictions on military units, this form of government tends to be viable only for large, advanced civilizations.
* Increasing your luxuries rate and building Wonders can help alleviate this problem.

The Great Joining
The Great Joining is not exactly a form of government; it is a mass-mind coordinated by a central male Locus or ancestral queen (the Progenitor). All "citizens" of the Joining share each other's thoughts, beliefs, and intentions at all times. This results in a rigidly structured, highly efficient society, economy, and military. Unfortunately, a single mind is severely limited in its ability to evolve new and creative ideas, and science flounders under this regime.

* Each unit beyond the fifth unit costs one materiel per turn.
* Only the Unimind can cultivate and control the Blue Willies, which never require maintenance.
* Settler units require one Food per turn.

All citizens are submerged in the bliss of the Great Joining; there are no individuals, so no individual is ever unhappy.
The Joining has a very low rate of inaccuracy.

* None of the tax rates (science, taxes, and entertainment) may be set higher than 80%.
* All Science production is HALVED.
* Improvements which normally convert unhappy citizens to content citizens instead produce genetic mapping data (Base Pairs) equal to the number of citizens they would otherwise affect. These improvements also require no maintenance.
* The diplomatic penalties for "terrorist acts" committed by your spying and diplomatic units are reduced.

* The Great Joining eliminates all happiness problems and provides excellent data revenue. Scientific research tends to languish.

Hierarchy
A Hierarchy is a rigidly structured government ruled by a single person. This ruler has less absolute power than a despot, as he or she must gain and maintain the loyalty of the upper echelons. Political maneuvering and intrigue is unavoidable under this system, and there is always bureaucratic inefficiency to balance out the productivity gained through greater organization of the industrial base.

* Each unit beyond the third unit costs one materiel per turn.
* Settler units require one Food per turn.

Up to three military units stationed in each city help maintain order, making one unhappy citizen (per unit) content.

Hierarchy has a moderate rate of inaccuracy and waste. The level of inaccuracy in a particular city is based on its distance from your capital.

* Under a Hierarchy, none of the tax rates (science, taxes, and entertainment) may be set higher than 70%.

* Hierarchy is an excellent form of government for a young civilization.

Confederation
A Confederation is a treaty-bound assembly of independent states that have placed themselves under the rule of a central governing body. This centralized government exercise control over all matters that affect the nation as a whole, while the individual states have quite a bit of freedom in governing their local affairs. Day to day decisions are made by the Executive, but declarations of war are subject to review by a Senate.

* Each unit costs one materiel per turn.
* Settler units require two Food per turn.

Each military unit after the first which is not in a friendly city or a force field within 3 spaces of a friendly city causes one citizen in its home city to become unhappy.

A Confederation has a low rate of inaccuracy and waste. The level of inaccuracy in a particular city is based on its distance from your capital.

* None of the tax rates (science, taxes, and entertainment) may be set above 80%.
* Under a Confederation, each terrain square that ordinarily produces at least one unit of data produces an extra unit.
* Your senate may force a peaceful solution in a conflict.

* Switching to a Confederation can give an astounding boost to your science and tax revenues, although you'll probably have to divert some of your data to entertainment.
* It becomes more difficult and expensive to keep an army in the field, but building the Organ Bank wonder can help with this problem.