Not directly from iTunes, no. iTunes only supports iPods. Depending on the MP3 player and how it loads tracks, though, you may be able to load the player manually. Some such players mount on the computer as if they were a USB flash drive volume and you just drag the tracks to the player. If the player requires specific software, though, either its own or Windows Media Player (as some players do), then you probably would not be able to use that player on your Mac (unless you're running Windows on it as well)
Note that if the player only supports MP3, you would have to convert any tracks purchased from the iTunes Store since they're all AAC, not MP3. The same would apply to any tracks you imported from CD unless you imported them as MP3. Check what formats the player supports; if it supports AAC (it may list MPEG-4/MP4 as a supported format; that's AAC) then it should handle any tracks from the iTunes Store with the exception of any copy-protected content from the iTunes Store.
Regards.
Message was edited by: Dave Sawyer