The English-language newspaper Bangkok Post has been updating on the flood situation.
This Google Crisis Response page has a map with flood updates as well as lots of information and emergency links.
For the Twitter literate, a good BKK flood hash tag is: #ThaiFloodEng
Lonely Planet author @CatherineBodry has been tweeting about the floods. Other helpful Twitter accounts: Patrick Winn, Bangkok-based Southeast Asia correspondent for the Global Post: @BKKApologist and Zoe Daniel, ABC correspondent who tweets as @seacorro.
Trendsmap is a good way to get an overview of the trending topics on the floods.
Thai Travel News is also a good resource for traveller updates.