Overclocking is a great way to save money.

When I built my PC a few years ago I wanted an Athlon XP 3200+ but it was $130. So I instead bought a $75 Athlon XP-M 2400+ (Mobile CPU, but it is exactly the same as the 3200+ except AMD set it to run at 1.4Ghz @ 1.4 volts) and OC'd it to 2.2Ghz/1.65V, the same speed and voltage as the 3200+. Saved $55