I just signed up for the Dopplr beta, so far it seems pretty cool. I think it will be ever more helpful when more of my friends sign up for it and we can coordinate our travels. I have a few more invites, so if you want one, shoot me an email.
I also have unlimited invites for the Joost beta. Right now it only works on Intel Macs and PCs. If you are interested in an invite, let me know. Over the past couple months that I've been using it, the amount of content has exploded. It still doesn't have everything I watch, but it definitely does have a bunch of interesting shows on there.