Pages, Numbers, Keynotes, the Apple version of MS Office. Take a while to get used to, but now that I've been using them for years, it really is better than MS Office unless you're an accountant and need the full power of Excel. Especially good if you have an iPad or iPhone, you can access your papers and stuffs and it's synced via iCloud to all apple devices.
For general software, look at Pixelmator. It's kinda the poor person's version of Photoshop. It does all your mid-range photo and graphic editing needs, doesn't cost anywhere near as much as Photoshop Elements or Photoshop. I bought mine years ago for $30 and it's been one of the best purchased ever.
And lastly, Omnigraffle. Once in a while you'll have a class that need graphs or charts, Omnigraffle is awesome. Depending on your major, you might not need it. I think they also have a trial 30 days thing if I remember correctly.
Those will pretty much get you through all the generic things you have to do in college.