I recently bought a 4GB Sansa Clip to solve the problem where once-a-week or so I want portable music or podcasts and don't have any: namely, at the gym, occasionally when walking somewhere, and on trains and buses. I've been looking for something exactly like this for ages--small, attachable for use during exercise, enough space for a few hours of music/audio, OGG support, and not necessarily much more than that. Basically, an iPod Shuffle that plays OGG and doesn't involve dealing with Apple. For the longest of time, this was pie-in-the-sky nonexistant.
After a few weeks of using the Clip, I'm extremely pleased so far. The battery life is much longer than I'd ever want to listen to music for continuously (they claim 15 hours, and I haven't gotten it down to less than half charge yet). It's light in the hand but not too flimsy in feel, the clip makes it easy to attach to e.g. shorts, the interface is easy to use, and the sound quality is good. After upgrading to the latest firmware, it plays OGG as well as MP3. Both Rhymthbox and Banshee work for transferring files to it.
I think my biggest complaint so far would be that the audio jack doesn't fit in as securely as it could, which sometimes manifests as sound skipping and can be fixed by making sure the headphones are completely plugged in. Seriously, it was funny when my Walkman skipped during runs in 2003, but I hope I'm past that phase of life at this point. At any rate, it doesn't happen all that often, so it's more of a minor annoyance than anything. And well, the firmware isn't free--but hey, can't have everything.