Western Plaguelands, in the Eastern Kingdoms continent, is a decent place to farm Blindweed. A stack of Blindweed goes for 10-50 wow gold in the auction house. If you have flying, Cataclysm and of course the wow herbalism profession you should be able to farm 1-3 stacks of this wow herb in one hour. The best place to farm Blindweed is Feralas.
The best addon to use for wow herbalism is Gathermate2. If you use Gathermate2_Data you will be able to see all the herb node locations for all the herbs in wow.