Generally any phone capable of AT commands or IrMC should be supported. Also any Nokia phone using Nokia OS should work. For Symbian please check separate topic. You can check other user experiences in Gammu Phones Database.
For information how to configure your phone, see Configuring Gammu FAQ.
Forget about using standard phones, they tend not to be reliable for long time connection to PC. Best option are GSM (GPRS, UMTS) terminals/modems. The best option seem to be Siemens modems (eg. ES75/MC35i/MC55i). Slightly cheaper, while still good are modems made by Huawei (eg. E160/E220/E1750/...). You can check other user experiences in Gammu Phones Database.
It depends on used operating systems Series40 and older phones should work (see How to configure Nokia phone? for information how to configure them), Symbian based phones are covered in separate topic, check Are Symbian phones supported?.
You need to install applet to the phone to allow Gammu talk to it. For older phones (Symbian 9.0 and older), install gnapplet (see Gnapplet Protocol). Newer phones can use Python based applet called Series60-remote (see Series60 Remote Protocol). This option is supported since Gammu 1.29.90.
Unfortunately no at the moment. Any help in this area is welcome.
Unfortunately no at the moment. Any help in this area is welcome.
Unfortunately no at the moment. Any help in this area is welcome.
It depends on your phone. For Nokia or AT based phones, you can try Gnokii, but Gammu should be superior in most cases. For Symbian phone you can try using Series60-Remote, which works pretty well with S60 phones.
If you are looking for synchronisation, try using something what supports SyncML to retrieve contacts or calendar from your phone, for example OpenSync or syncEvolution.