Either I am a complete moron, or this is one of the greatest skill improving sites on Earth. No, it's not Web 2.0 and all flashy, but FSI gives you a free way to improve your skills, add to your personal worth, and finally, learn something incredibly beneficial.
Ok, enough intro. FSI is a public domain site that actually teaches you how to speak foreign languages for free. The program is contributed to by the U.S. government of all places and your lessons are either text based or played over the PC in an MP3 format. Some of it is still in development but a few languages are ready to go.
Here are a few of the languages they list:
To add to the usefulness of the site, it supports RSS and calendering. I seriously cannot believe this site is not used more often. Check it out at FSI Language Courses.