I have an interest in grammar (duh). I like knowing how the grammar actually works instead of simply relying on the ol' "Well, that sounds right and that sounds wrong" test. Thanks to NPR, I learned about someone who talks about grammar too--Grammar Girl.
Grammar Girl provides both an online resource for people like me or for those who truly wish to understand grammar and improve their writing. She also has a podcast which is interesting, short, and is a great resource for those who are teachers--the podcasts are typically between two and seven minutes. (For a high school teacher, it might be fun to have a weekly grammar lesson based off the podcast. It wouldn't take more than about fifteen minutes, and could engage students a little more than perhaps other methods).
There's also another podcast that teaches you Spanish in 15 to 20 minute segments--or a coffee break--hence the name, Coffee Break Spanish. That's just really cool. My boyfriend and I are going to Spain, so we may use this to brush up on Spanish--him to learn, me to review the basics (I have a BA in Spanish).
The Internet really does seem to expand our opportunity for learning new things!