If you've never heard of Hulu, then you are truly missing out. It's completely free, legal, and doesn't have the crappy buffering like on Funimation's site. However, they're only allowed to put up episodes two weeks after it airs in Japan and there are a couple of short commercials here and there. Also, the site is US-only, but there are ways to get around that.
Basically, if you absolutely cannot stand the buffering on Funimation's site, then you should check out Hulu.