I'll probably get mine either though school or my wife's work. Not sure yet. I second the idea about catastrophic only coverage - it seems the way to go for most students I think.
External hard drives are pretty cheap these days - I'd get something that's as big or a little bigger than your laptop HD, that way you can backup your entire hard drive to it.
Another option is to buy an external enclosure for a normal laptop or desktop drive and use it externally - handy if you've got extra drives laying around not being used:) Also, if you are super ocd about being sure your laptop is never down, you can use a drive that will work in your laptop as backup (most laptops take 2.5" drives) in an external drive and ghost the entire laptop drive (OS and all) to the extra drive. That way, if the laptop drive fails you just take the extra one out of the enclosure and stick it in the laptop. Probably more work than its worth, but its an option.
Processor speed likely won't matter at all for anything school related, its really only a factor when messing with picture/video editing and gaming etc.
Many laptops these days are available with various features to make them more damage resistant (things like suspended/cushioned hard drives, hard drives that sense movement and park the head before impact, metal or otherwise really strong frames/cages etc) which would probably be worthwhile on a school computer. I at least will be carrying mine around on a bike and will probably bang it up a bit.
Hard drive speed and ram will make a difference in how quickly applications load and do their thing. If you can, opt for a 7200 rpm hard drive and ~1gb of ram. It will work just fine on a 5400 rpm drive (the norm for laptops), just take a little longer.
A USB thumb drive is always handy for file-transfer and quick backup. You should be able to easily find 1gb models for ~$50.
Built-in Wireless (802.11) is a huge plus as the integrated wireless cards work much better than the aftermarket wireless cards you stick in the PCMIA slot (or whatever the acronym is).
Note, I don't know a thing about Mac's and what I say applies generally to most PC based machines, but might not apply to mac's. Also, I claim no special knowledge of computers, so there may be other options I'm unaware of bla bla bla...
A little bit of a generalization here