I use an Ipod shuffle 3rd generation.
I know those who are familiar and accustomed to Ipods complain that you can't buy different headphones for this model (if you aren't familiar with it, the controls are not located on the player but on the cable wire of the headphones).
To me it works because it is super light and I can't even feel it (it's smaller and thinner than a regular lighter). It clips on directly to my clothes so I don't need any strap bands, holders etc.
I have over 400 songs organized into playlists, still have memory available, and it's enough for me to have an entertaining workout.
I have both yet prefer the new Ipod Nano for running rather than the MP3. Bought an Sansa MP3 from Best Buy years ago, and its ok. The Nanos also have the radio functions and if really bored while on a bike or something, you can view video as well. Also have an Ipod Gen 4, which is excellent for just about anything. Apple is just far superior, hands down in my opinion.
2000 St. Patrick's Day 10K, Washington, DC
2000 Motorola 10K, Ft. Bragg, NC
2000 Fort Bragg 10-Miler
2000 Mother's Day 10K, Ft. Bragg, NC
2001 St. Patrick's Day 10K, Washington, DC
2001 Lynchburg Half-Marathon, Lynchburg, VA
2001 LaSalle Bank Chicago Marathon
2011 Firecracker 5K, Huntsville, AL