I have been using an older Palm III cx running Portalog
) for casual
operating or Golog ( http://home.earthlink.net/~david.ek/golog/
) for contesting.
What I like about Portalog is that it has flexible export capabilities (ie you can choose to export only a subset of your QSOs on Hotsync) and the data is automatically converted over to ADIF when it is synched, which makes for an easy import into your main logging program on your PC.
I often operate QRP CW contests Pedestrian (ie walking) mobile with my Elecraft KX1 in my hand with the Palm III attached to the bottom of the rig with an elastic band.
For portable contest operations from a picnic table I often use a Palm keyboard with the Palm III as it makes data entry a bit easier. These can be found NIB on eBay for older Palms for as little as $10.
You don't need a high end Palm to run either of these programs and they work very well and give you many, many
hours of logging on a couple of AAA cells.