KissTunes: make music online, with your keyboard
The "kiss" in KissTunes probably refers to a show of affection, but it could also very well stand for "Keep it Simple, Stupid!" KissTunes isn't a complex compositional tool, and it's not aimed at professionals. It's more akin to a greeting card, except instead of sending cheesy canned music, you play and send the music yourself. Obviously, this isn't going to revolutionize the Internet, but it's a fun idea.