Last week my boss gave me a PC he had received with a bad motherboard. "There are some blown capacitors," he said, "but maybe you can use some of the other parts." I decided immediately to use it as a learning experience: it was time to learn how to replace capacitors!
I ordered the replacement capacitors from digikey.com, and as soon as they arrived I soldered them in. I plugged in the PC and heard a piercing, high-pitched whine from the power supply, which told me there was a third blown capacitor - awesome - but a quick switch with a known-good power supply demonstrated that my soldering job had worked.
Today, feeling very empowered, I grabbed every old, broken motherboard I could find and checked for bad capacitors. There are about a dozen capacitors now in the mail, destined to fix two PCs and a power supply and gain me a lot more practice.