I just got a JBL On Stage 3 Portable Speaker. I like it.
It runs on the mains or on six AAs, and the sound is real dang powerful for the size, good both for podcasts and music. I've never before heard anything this size sound this good or loud.
I like it for when I'm not around one of my speaker systems, but I don't want to wear earphones, they are not always practical.
It takes various shapes of iPods, and it also has a regular small sound-in plug so you can use any device. (It comes with a short male-male cable.)