[Yeri]

EDPnet, a smaller ISP has been natively providing IPv6 for ~3 years already (but 3rd biggest independent ISP?).

Telenet followed somewhere last year, and Belgacom (biggest) followed this year (only on new modems though).

[ay]

Voo is doing IPv6 as well, AFAIK.

http://www.worldipv6launch.org/measurements/ gives a per-AS breakout, with the %%% being the massaged number as seen by the content-provider participants.