All these have been used, are still being used, or were tested by me at some point.  Some of the review type comments are borrowed with acknowledgement from Dr. Robert Oh's Palm Medical website.

HanDBase
This is a relational database that can be easily modified by any user. JFile was the original Palm database, but I believe that HanDBase is much more powerful and useful in medicine. Perhaps the most useful database that can be made is a Procedure Log to track your procedures. Because of it's relational capabilities, it can also be made to track hospitalized patients, or be a check out list if so desired. There are many powerful tools HanDBase can be used for, and it's database application in medicine is only limited by your creativity. Can convert into Access, Filemaker, or Excel documents by it's desktop version (included). For examples of what it can be used for, check DDH Software gallery of HanDBase files.

SD/MS? Yes (make sure you place your actual pdb database files on your PALM to backup!)

Documents to Go
Always bummed about the memo pad not being a functional/useful word processor? Wish you had the capabilities to view Word/Excel/Powerpoint files on your Palm? Well, guess what, Docs To Go is just for you! Although somewhat expensive, if you buy a new Tungsten, it will come with the latest version of Docs to Go. Excellent program, almost a must have. Also able to read Palm .doc files. Backup is also seamless and works on your memory card or on the Palm. Works great, may be able to surplant need for a Doc reader in the near future!

Document Reader: iSilo or TealDoc
Palm docs are small documents that take up very little physical memory. However, to read .doc files, you must have a Doc reader. There are many out there on the market, to include Docs-to-Go, however, I also recommend you having another doc reader, as Docs-to-Go does not have the full capablities to take avantage of .doc files with bookmarks and certain graphics. TealDoc is good and reasonably priced. iSilo is also a very popular doc reader and can read HTML files. Try them both, determine which is better.

Launcher
The current Palm application launcher is not the best. Launcher III, a program for Palm OS 4, was one of the BEST launcher programs out there. It made your Palm a "tab-based" launcher, which makes it very quick to navigate by using one less penstroke. With the launch of Palm OS 5, Launcher has evolved to "X". It's expensive for a launcher, so demo it and see what you think!

X-Master
Formerly known as Hackmaster, this freeware program can be helpful for those with Palm OS 4.0. It can add functionality if you would like a Screenshot program to capture screenshots, or change the backlighting, or add a "pop-up" menu for favorite programs (PhlegmHack), or increase the clipoard character limit. Does NOT work with Palm OS 5!

Epocrates Rx
The true “killer app” of Palm PDA’s. You cannot do without this program. Designed from the ground-up for use on a handheld, with simplicity and speed. Truly one of the few programs that saves time for the busy clinician. I refer to this countless times just even to “double-check” doses, especially for kids. It's free, however, Rx Pro version is bundled with an enhanced version of Rx (with helpful ACLS tables, etc, and an alternative medicine database), qID and MedMath (see below). Frankly, in my opinion, don’t bother with paying $50 bucks for these features, it’s not worth it. Updates via web, which is also the beauty and elegance of Epocrates. Why upgrade every year, when new drugs/info can come out daily?

SD/MS? NO

5 Minute Clinical Consult
5MCC is probably the most useful Palm book I have used. Just like the book, it gives bullet points of the basics, the diagnosis, and treatment of tons of diseases. It works very well in Palm format, since you are looking at it for a quick reference, not reading it for a long time. Interface is excellent, and it's search capability lends itself to quick reference. Highly recommended for any physician involved in clinical care. Several companies sell this, including Skyscape, which can package other books/PDR with the 5min CC; Handheldmed, and Franklin.

SD/MS? YES

The Wills Eye Manual 3E + The Wills Eye Drug Guide for Pda
Really the only commercially available Ophthalmology programs for PDAs but still incredibly useful for all that.  A must for Ophthalmology residents and most general ophthalmologist if not all ophthalmologists, particularly the manual.

GAMES

Bejwelled from Astraware
Probably one of the most addictive games for your PDA.

Bookworm from Astraware
A very fun word game.

Zap 2016 from Astraware
Still one of the best arcade type games for your PDA.