David, I can tell what not to get...
I bought a HP Ipaq 6515 at one point in time - it was a brilliant concept - converged PDA, phone, GPS, etc..
The problem with it and the prior model that I upgraded from was the incessant need to reset it at times nearly every hour. IT wouldn't run third party software at all well - typical m$ imMobile v5 crapware, as a matter of fact it couldn't even run its own software - I'd get a phone call and could not answer it, not for quids, push the soft key on the screen - no joy, same for the green button on the set itself, would end up having to reset it and ring back, most infuriating at the time, for the money that you pay for them they are just not worth the aggro. In the end it had pissed me off so badly I was about to throw it on the ground and stomp on it, but I thought better of it and took it back from whence it came and demanded my money back, this happened all within the space of 10 days of use!
Not to mention crappy hardware as well - within the first hour of use the belt holster clip rivets sheared off and the PDA half of the holster fell to the ground, fortunately without the PDA in it, it got caught on the seatbelt on the way out the door of the car. The only thing securing your then $1200 PDA to your belt were 3 x 3mm 'plastic rivets', no solid metal here to protect your investment as once you drop it - your warranty is history, I suspect it is part of the game plan to sell more PDA's, they blame it on you for not being more careful when the reality of it is that mobile phones get bashed around, they get dropped, they know this but they do not engineer it in to the design of the device.
I couldn't get it to sync using synce to linux either, it is a windows only machine. The work around for this was to save everything you did on it to an SD memory chip and get an SD card reader to pick it up using linux.
One more thing about it was that I bought it for near $1200 from H N, in the space of time that I had it the price had dropped by $300, definitely do not rush out to buy one, and if you buy one make sure you shop around real hard, e-bay is a place to look but be vewy, vewy careful.
I had been looking at the palm treo 700, they are good and do interface with linux, but the camera VGA resolution is a bit poorly considering the money that you pay for them.
In the end I gave up on the PDA phone idea and got a '3' Mobile LG 880U camera phone with near the same level of functionality for far far less of a cost - it was a throw in with the connection for a year on a $45 a month plan.
As to finding what you need, google for PDA on google, you'll find a myriad of choices there.
Cheers, Nick Tomlin. -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html