Friendly can be a bit subjective. The one you've started with is practically based on friendliness, so you're probably fine there. To a certain extent, admins tend to set the tone for the group, especially the founder, so looking at the admins helps.

I'm not sure if this qualifies as a friendly group, as it has over 450 people, and I'm sure some of them aren't friendly, but either way, you might look at my main group, Twilight's Library.

Specifically, take a look at the front page. If you scroll down, I've got a large, categorized list of notable groups there that I'm still working on adding groups to, and I'm sure you'll find a few groups of interest. You might like Twilight's Library, too, as a very large categorized collection of fanfiction. I'm not going to guarantee everyone there is friendly, but I run it, so things shouldn't get too bad there.

Now, there are several groups that are on specialized topics that have friendly people if you are interested in that topic.

For example, the Twist group. There are only 18 people in this group, but most are friendly. The Apple Bloom group is fairly friendly as well.

Now as far as helpful groups go, you might check out The School for New Writers. There are a million threads over there with lectures on how to become a better writer. And they will grade your fanfiction and tell you how good it is. They may be harsh when doing so occasionally. But, you know, when you are learning how to write, having people that are willing to pull apart your work and tell you exactly what you did wrong is nice.

And how about Authors Helping Authors? It's based on an interesting idea.You submit your fics there. People in the group review your fic. And you are then obliged to review one of theirs. If you're looking for feedback on your fanfic, it's a great idea.

I'm sure there are others that could be added here, but this post has gotten long enough. Hope it helps...