Yes, these VZ sides are rather popular over here. But, and I really feel like pointing it out: it's a bit like Russian Roulette.
Apart from the fact that a future (German) employers might search there for you and find things you rather not have them to know (once you registered people can upload pictures and name you on them. These pictures might not always be in your best interest too), but that's just one of many things about it.
I don't know how good your German is, but this is a rather in-debth article on the topic:
http://rettetdiewelt.blogspot.com/2007/03/interessantes-ber-das-studikz.html
Of cause there is an abridged version on Wikipedia:
http://en.wikipedia.org/wiki/StudiVZ
and as far as a quick comparison goes this side says almost the same as the first one, only in English:
http://www.karsten-wenzlaff.de/?p=115
I don't want to say that you shouldn't get an account there, I just want to state that there are a few things you should check before you do and ask yourself if you are okay with that, cause personally I know a lot of people who deleted their accounts lately...
And personally I am rather sceptically toward Lokalisten too.
The whole idea is that you get an account, search for people around you and than you can try to figure if there is someone who might already know the date you are going to meet that night and can tell you something about her... or something like that.
To me it sounds rather silly and I am not sure if there is a value for someone outside Germany. (if you wonder why: every German university has a version of StudIP. you enroll into your courses there, get PPTs from the lectures and stuff and you they have a smiliar feature. It's fun for a minute or two, but seriously: it's kinda useless. StudIP used to be really important, until the VZs came along. Only downside is that you can only get an account if you enroll into university...)
But hey, that's just my personal oppinion.
Other ways of practicing German could be:
Youtube. I regularly stumble upon German commants. If you know what's big in the charts right now, you are likely to find some. BUT: some people write in a horrible internet slang and with so many grammatical mistakes, it's sometimes really hard to decifer them - even for a native German speaker.
And maybe sides like Livejournal or one of the other Journals might help you. You can find communities dedicated to German and from there on it is rather easy to find People writing German. Of cause, you don't need an account and it makes you a little of a stalker, but it's kinda useful.
And: if there is something you are aspecially interested in just try google. We have a lot of boards. Just we don't call them boards, we call them "Forum". Some are really big and rather active. Of cause you find a number of people writing horrible German too, and some areas are just for fun and rather senseless, which might confront you with a lot of slang, but it's worth a try anyway, right?
And a rather usefull and free side that's really popular among Germans and that's going to be usefull if you aren't sure what your favorit passtime is called in German, just try:
http://dict.leo.org/
