Here’s a quick idea I had while chatting with someone in Australia via instant-messaging this morning.
I would like to see a plugin/extension for Gaim (or any other instant messaging application, but especially Gaim, since it’s the one I use) that showed the local time zone of the person you’re chatting with in the chat window. Here’s a quick mock-up:
I’m not looking for anything too fancy. I don’t mind setting the time zones for my contacts manually (though tying this in with a system-wide address book makes sense in the long run). Also, it shouldn’t show anything if I haven’t set a time-zone for a contact, or if we share the same time-zone.
This would keep me from interrupting Nick during his dinner time in Paris.

Occasionally I will get an email attachment from someone compressed in a .SIT archive. This 