I've been working remotely, doing primarily development and architecture work, for the past 24 months. During this time I've used quite a few different communication mediums, each of which had their strengths and weaknesses.
Emails are the primary way of communicating. They are great for keeping track of what was said, clearly thinking out and stating a point, and useful for managing work.
Instant Messaging (IM) is very useful for a quick back and forth discussion: "how do you do X?", "can I checkout Y?", " I can't access Z, is it down?" Again, you have a full searchable history of what's been said which is very useful. If you find yourself chatting for more than 30 mins then you should probably have made a phone call. You also need to be careful not to slip into idle chatting which can be counter-productive (for both parties!). You can however, answer in your own time and you can flag yourself as busy if you don't want to be disturbed. Also, Skype client offers encryption which keeps everything safe.
Voice/Skype Sometimes a 3-day email back and forth could be easily solved by a 10 minute phone call, particularly something like talking though a business requirement with a BA. And it is good in the remote development world, to have a regular voice conference call/team catch-up. I used Skype because it is free, and free is good!
Collaborated Documents I have started using this with my "To Do" spreadsheet via Google Docs. It is not yet proving super-beneficial but I think that over time, once we adjust to think this way, it will offer a lot and save a lot of to-ing and fro-ing of document versions. I've used collaborated docs to good effect with bug lists.
Wikis These are super-useful. Typically have one per project. Source control, all project documentation, bug lists, project "how-tos" etc. People end up using it because they are just so darned easy to update! All those 1/2 to 2 pages documents end up being written in here. If your team are slack at documenting then try introducing a wiki! My only gripe (as a team member) is that it is not so easy to throw it on a flash drive and take it away with you when you leave.
Twitter Played with this for status updates but it didn't stick.