The Filter, a plug-in for iTunes that parses your iTunes library so that you can generate a cohesive playlist instantly by selecting a single song as a starting point, released a Nokia Series 60 version last month, and this week, added a Mac version. (Although the program was originally designed for iTunes, a Windows Media Player version is in the 'alpha' stage.)
I like the way The Filter gives you a simple interface for the complex work of automatically assembling a playlist. One particularly good use for it is for auto-filling your iPod with a new set of songs if your music collection is larger than your iPod. For instance, if you were on your way out the door to the gym the way I should be, you could pick your favorite workout song, generate the playlist within iTunes, and transfer it over to your iPod Shuffle.
A representative for The Filter told me that over the next few weeks, the Filter website will be revamped to give it "a more music-orientated focus, with YouTube video, artist profiles, etc."
