If you bought a budget-level notebook within the past year, chances are good it came with Windows Vista and 1GB of RAM--a poor combination to say the least. Vista needs at least 2GB to operate efficiently, especially on notebooks with integrated graphics processors (which borrow RAM from the rest of the system).
Newegg.com has a Transcend 2GB PC2 5300 notebook memory module for $26.99 (after a $10 mail-in rebate). Shipping will run you $4.99.
You'll need to make sure, of course, that your system can accommodate this kind of module (it's a pretty standard size and speed). And check the manual to see what kinds of memory configurations it requires. For instance, it's not always possible (or advisable) to mix and match modules, meaning you might not be able to plug in the 2GB stick alongside the current 1GB stick (if that's what you have--your system might have a pair of 512MB modules). In short, you may need to pull your existing RAM to make way for the new module--but, hey, that's what eBay is for, right?