I've been considering
The IPAQ 6915 which is capable of all of the above plus it has built-in GPS so you can install TomTom Navigator on it and stick it in your car when travelling.
Another one that caught my eye was
The Fujitsu Pocket Loox 830TN.
Both are a bit bulky as a phone but are quite feature laden as PDAs. Both run Microsoft Windows Mobile which is quite usable now but has its own limits. There are 'Push' e-mail services available for it so you can use it to send/receive e-mails on the go like the Blackberry.
People have managed to get
Lunux running on an IPAQ so if you are feeling adventurous you could attempt something like that. I don't know if it will work on a 6915 though. Another project called
Familiar is being worked on that may support more handhelds.
You can also try running
Pocket UAE on it. I did so on a different (windows Mobile 2003) PDA and managed to get the game Cannon Fodder and a few other things running :-D
