http://langintro.com/kintro/
Step-by-step introduction to the basics of Korean. Contains sound embedded so you can listen and repeat what's being taught. Brilliant learning guide.
http://www.interedu.go.kr/indexe.html
Nice site set up by KOSNET. Requires registration(free) but worth it.
Fairly slow site, though, takes ages to load up the pages. You can download the coursework, though, which makes up for it.
http://en.wikipedia.org/wiki/Korean_language
Wikipedia's entry on Korean, contains a lot of useful information, and a list of links to places where you can learn the language.
[edit from Hobbes]
Thanks Lantis. For new posters, any off topic posts to this thread will be moved to a seperate thread. Try to keep this thread clean. ^^