If you've got a Frys or Micro Center nearby, pull your drive, drop it in an anti-static bag and take it down to compare to the bare drives they'll have in stock. Find one with the same dimensions and see if it will be compatible with your mounting hardware (take your drive sled / check the screw holes).
You can shop online, in theory any PATA 2.5" laptop drive should work. You might find that practice is another matter, though.
Don't forget the thermal situation - if you replace a 4200rpm drive with a 7200rpm model, you'll be dumping extra heat into your laptop.
If you've got a 60GB drive now, I'd be surprised if you could buy a drive bigger than your hardware / operating system will support. The two limiting factors will be what your BIOS will let you boot from and what your operating system will support.
Speaking of operating systems - do you have restore / install discs? You'll need to either reinstall or migrate your existing installation to the new drive. You might want to pick up an external USB enclosure for your old drive, it'll make the process easier.