For my work I am at different locations for different projects. Sometimes I work at clients with complete internet access, but most of the times we are behind firewalls and proxy servers. I like to keep in touch with friends and colleagues by instant messaging now and then. Normally I use Pidgin, but this doesn't work if I am behind firewalls and proxy servers.
Ah, up until yesterday, because yesterday I discovered Meebo. With Meebo I can login to different instant messaging accounts like ICQ, GoogleTalk, MSN and AIM. Once I am logged in I can open new chat sessions with all my friends and colleagues right from the browser. And because I do it via the browser I don't get in trouble with firewalls and proxy servers.
Update: And now Meebo also has a Firefox addon, which makes it even easier to use Meebo.