I need to put together a portfolio for college and I came to a screeching hold when I realised I have no idea what to put into a game designer portfolio. Do I need to put in artwork, writing, what? So can anyone please help me here?

I would say put in any and all work you can that relates to what you want to do. Do you want to be an animator? Well, put in drawings, concept art, rough animation drafts, ect...

Programming? Put in some code works you've done, some systems you've messed with, code examples.

Basically, whatever you put in there, be sure to show the steps taken to do so. At least, this is what I did for my Web Design portfolio.

Also, as a hint, if you're required to make a Business Card / Logo, don't do the boring thing and use your initials. EVERYONE does that and its a shit way to stand out.

I'm not at all familiar with what schools are looking for in a game design portfolio, but my Bachelor's Degree is in digital art/graphic design and I work as a web designer, so maybe this can serve as a start? My college portfolio review consisted of the following:
-a self-portrait (this was my college's only requirement, the rest was up to me)
-a couple of still-life drawings and paintings
-a short comic
-photos
-previous graphic projects from high school
-examples of web sites I've made for clients (this was primarily for the second college I went to to get an additional diploma in Web Design, but it couldn't hurt to learn some HTML and CSS in the future. Art portfolios are moving online and making a kick-ass website helps you stand out)

And I managed to pass no problem. The key is to show variety and proficiency in a variety of mediums and styles. I can't tell you how many people I've talked to that wanted to get into the same program I was in, but the majority of their portfolio consisted of anime-style drawings. They were rejected since it showed mastery in only 1 style.

Hope this helps you in any way.

A game. I'm serious. Go to game maker, make a game and put it in. Even a one level Galaxian rip-off with one unique feature will speak more about your design than any kind of picture or document. You don't apply for business school with paintings right?

Other things to consider:
An application you coded yourself
Any kind of creative writing
Mods to an existing game/engine
Something showing skill in 3D design

That's what got me in.

I'm a programmer, not a designer, so I'm afraid I can't offer any particularly specific advice, but I've got to say that this:

ImmortalDrifter:
A game. I'm serious. Go to game maker, make a game and put it in. Even a one level Galaxian rip-off with one unique feature will speak more about your design than any kind of picture or document.

is an excellent suggestion :)

Thank you for the advice. :) I was panicing a little and I've got a good idea what to put in it now