I've liked what I've seen with Documents to Go. AvantGo - Simply put, AvantGo allows you to grab information from the Internet and pull it down to your Palm device whenever you hot sync. Very handy for grabbing news, sports scores and stock info. Using AvantGo makes it very easy to run up against the 2 megabyte storage barrier and will make you wish you had opted for the 8 megabyte device. Free and essential.
Hacks can change screen highlighting, save battery life and do many, many other things.
Hackmaster, free, is essential for any of the hacks. Outliners really reflect the way most lawyers work. BrainForest may be the one program that convinces lawyers of the utility of the Palm devices. BackupBuddyNG - Excellent backup utility. I feel much better with Backup Buddy on the job.