Any laptop or Netbook that's more than a few years old is probably running out of storage space right about now. These days, it's tough to get by with only, say, 80GB or 120GB.
Time for an upgrade! Newegg has a Samsung Spinpoint M7E HM501II 500GB laptop hard drive for $49.99 shipped. That's after applying promo code NBHDDSALE3 at checkout. (As with most Newegg codes, you must be a newsletter subscriber for it to work.)
The drive runs at 5,400rpm, which is probably on par with the drive you're replacing, and sports a SATA interface. If you're upgrading a really old laptop, check to make sure it uses SATA and not IDE. (Only systems older than 4-5 years are likely to have the latter.)
Keep in mind that you can't just install this drive alongside the existing one; you'll have to swap them out. That's usually a pretty easy piece of laptop surgery; the real challenge lies in cloning (i.e., copying) your existing drive to the new one before making the swap.
My advice: Buy an inexpensive external hard-drive enclosure (such as this one for $11.98, also from Newegg) and then do a little juggling. Install the new drive in the enclosure, copy everything over, then swap the two drives. After you've verified that everything works and your data is intact, wipe the old drive--now residing in the enclosure--and use it as secondary or backup storage.
Recently, Lifehacker explained how to do this in a feature on using free tools to clone a hard drive. There's some work involved, but the end result is awesome.
The Samsung Spinpoint is a bare drive (meaning no box, and probably no manual), and it's backed by a three-year warranty. Newegg's promo code is good until July 18, but the drive could sell out before then.
That's because it's one of the best prices I've ever seen on a 500GB laptop/Netbook drive. The last time I wrote about one, it was $78 for the same amount of storage. Fifty bucks is an outright steal.
Bonus deal: If you don't yet own the incredible Planet Earth series, here's your chance to get the first disc on the cheap: The Discovery Store has "Planet Earth: Pole to Pole, Mountains, and Deep Ocean" on Blu-ray for only $1.99 (with coupon code TBDVD199). Shipping adds $2.95. Too good to pass up!