[ALUG] What PDA to get for use with Linux?

My wife's Palm Treo is feeling its age in various ways and needs replacing. Currently she synchronises the Treo with Evolution in Gnome using the built-in Gnome/Evolution synchronisation software. So, what can we buy now to replace the Palm that will allow her to continue as far as possible in the same way? I'd prefer a solution that doesn't involve a separate server system/process, especially one 'out in the cloud', but apart from that we really don't have any major constraints. -- Chris Green