I've been a unix and network admin for a while now. I've had the pleasure of working with plenty of backbone providers, some of them seem better than others. One I absolutely love is Hurricane Electric. Not only do they have a free ipv6 tunnelbroker, you can take their test, I think I passed the sage level a few years ago, but they also have some other great utilties. Check out dns.he.net for some free dns utils. Some of you may already be aware of these awesome tools.
But my favorite is their bgp site bgp.he.net. You can type an ip, subnet, AS number or name in the search box and get tall kinds of good information. I setup a previous employer with an ipv6 subnet, then after I left I've used this tool to find out they decided not to continue advertising it. You can type your provider's name in there and get a feel for who they peer with, how many different connections they have, their IP subnets... it's pretty useful.