There are heaps of phones that can sync with Outlook but if you're going to be doing a lot of swapping of appointments and adding details on the device, think about what type of input system you'll need -- such as a QWERTY keypad to type fast messages or a touchscreen to drag and drop appointments.
Some options we'd suggest looking into:
All of the Nokia 6000 series phones come with PC Suite (Nokia's synchronisation software).
The Dopod 838 Pro is a popular (but relatively expensive) model, too.
Discuss: How do I combine my phone, PDA and iPod into one device?
Be respectful, keep it civil and stay on topic. We delete comments that violate our policy, which we encourage you to read. Discussion threads can be closed at any time at our discretion.