One easy fix - have every remote person call in to an open mic on either someone's computer or, say, an iPad that is set up with video. Then any ad-hoc chat gets captured by all the remote folks. But, it really is continual effort to get people in the chat room. It's up to everyone on the team to constantly remind each other to "take it to chat".
Yeah, this has helped us a lot. I am one of a few remote and when I can, I skype into a big screen in the central office. The account there is set to auto answer calls from its list of contacts so I can call in whenever I want. I often leave it open all day on a spare computer.
