I have a couple of Google Wave invites left, so let me know if you need one.
Although it still has a long way to go before you will want to use it on a daily basis (for one thing, it is slow), Wave is probably going to be an important communication and collaboration tool for some obvious reasons:
1. The platform is easily extensible
You can write a useful gadget in a couple of hours (Google Wave gadgets guide).
2. The server architecture is open to federation
Just like e-mail (Google Wave Federation – Why it matters).
3. E-mail is an outdated communication tool
4. It’s Google
Google has a lot of steam to power this transition – slowly but surely