Hey, I'm currently a first year at York and so I thought I'd contribute my opinions to this thread because I know it would have been really helpful to have had a thread like this when I was choosing last year!
Firstly, the official disclaimer, which I know everyone says but it really is true - no matter what college you are in, you will have an awesome time if you make the effort to get out and about and just chat to everybody you meet! There are some colleges which have a better social life than others but the difference really is minimal - and the majority of your social life will stem from societies which are not college exclusive (or so I have found) or the people you're living with, not the college's reputation for events/socials!
So with that out of the way, here are my opinions on the colleges at York!
ALCUIN
It has a reputation for being quite quiet and 'out of the way' but I've actually found it to be one of the more social colleges - the way that its lovely new accomodation is structured means that everyone congregates in the kitchen area so that you bond with your housemates easily, and a lot of my good friends who are outside my college live in Alcuin. There's also a lovely little cafe/bar there.
The accomodation is also for the most part very pretty! Lovely ensuites (some with baths!) and modern kitchens. It's also situated very near the library so good for those of you who might find it hard to motivate yourself to go and get books - if it's right there, there's no excuse!
It's also near to the Law, Theatre Film and TV and Chemistry departments, as well as the medical school. However, it's worth noting that the campus is really really small, you can walk one side to the other in about 10/15 mins, so don't worry too much about proximity to your department!
DERWENT
You will probably hear a lot about Derwent being the most sociable college, and it does deserve some of this reputation - they have 'Club D' events on a very regular basis in their bar, with themes ranging from chav to superheroes, and everyone seems to have a great time (though I've never been to one!) It's location isn't central - it's on the edges of the main campus, but as I have said this really isn't a problem, and it's very near a lot of departments - politics, philosophy, English and education to name but a few. It's also one of the prettiest looking colleges - it has lovely water features and looks gorgeous at the moment with all the snow!
I have no idea what the accomodation is like there, I'm guessing it's fairly standard - I haven't heard any complaints! I'd say Derwent is a safe bet (it's the one I put first on my accomodation application last year as well!)
HALIFAX
Halifax is a bit of an odd one as it is actually 5 minutes out from the main campus. It is however the biggest college so you are guaranteed to make new friends! Everyone I've met from Halifax seems to like it, and the way that accomodation is arranged in houses seems more social than the corridor system of the halls on campus. I don't know how nice the accomodation is though - again, I'm guessing it's pretty standard.
It also doesn't mean that you will be outcast from campus life if you live here, as some people might imply - as long as you make an effort to join societies/go to student nights in town/generally chat to people, you'll be absolutely fine! Quite a few of my friends live in Halifax and say while it's a pain being a little further from campus, it isn't at all detrimental to their social lives.
JAMES
Now, from tradition, I should proceed to insult this college because I come from Goodricke and we have a massive college rivalry - but actually one of my best friends at uni lives in James and I went to one of the best house parties ever there, so I can't abuse them too much!
James is notable for 2 things - its gorgeous accomodation, which is so so pretty with beautiful huge bathrooms and kitchens, and its lack of a bar, which doesn't actually matter now that we have a union bar for everyone on campus, not just college bars.
However, it does have a reputation for being a bit quiet! James usually joins up with Goodricke/Halifax for big events or socials though, so it's a good one for making friends in other colleges.
LANGWITH
Another quiet one - Langwith doesn't really have any sort of reputation for anything. Accomodation is decent, on the smaller side, but the rest of the college is very modern and shiny with lovely surrounding grounds. Most notably, Langwith features the new SU bar 'The Courtyard', which is really popular and hosts campus events which so far have been successful. Langwith is also quite central to campus and a lot of lectures happen there in the large lecture theatre. Langwith is another safe bet, I'd be happy to live there.
GOODRICKE
Well what can I say - Goodricke is the best college on campus without a doubt. To dispute this claim, people argue that our rooms were voted the worst in the UK for student accomodation - but worry not! Goodricke is moving in the summer to the brand new, modern, shiny campus which is being built ready for October 2009. This means you'll have brand new rooms, which will be either ensuite or non-ensuite depending on what you want, and better kitchens and general facilities as well.
Goodricke has deservedly had a reputation as a party college for years, and this shows signs of being revived this year with the new JCRC - we recently ran a social which had over 100 Goodrickers dressed in army gear and rampaging around the centre of York in its clubs! We also hosted a sell-out event earlier this term which was 90s themed.
The only negative in the past of Goodricke has been the hideous accomodation - but with the transition to the new campus this worry is removed, making Goodricke officially the best college on campus!
(DISCLAIMER: I live in Goodricke. My account may therefore be slightly biased..)
VANBRUGH
Vanbrugh is right in the centre of campus and is another really safe bet. Accomodation is standard, but there are some beautiful new buildings which Vanbrugh owns too set slightly apart from the college, with really pretty modern rooms and kitchens, and a nice quad at the front! It's got good events, a really great bar which is often the meeting point for society socials, and houses the History department so I spend a lot of my time there!
So there we are - my guide to the colleges. If you have any questions or want to know any more, please quote me and reply, or PM me!
Hope this helps!