Yep, they're re-released all the old D&D .pdfs, including a whole host of new ones, over at www.dndclassics.com.
At the start of the lifespan of 4e, WotC removed all the PDFs from their website, citing piracy and other issues as the reason they withdrew. 4e's sales suffered, especially as Paizo continued to release PDFs of all the new Pathfinder content.
I, for one, applaud this move - it's good to see that the OSR movement as picked up enough steam to be picked up by a company currently facing a lot of problems and sniping from all corners.
This should be interesting. I expect WotC's stock to rise in the next few months, just in time for the release of D&DNext...
EDIT: Apparently, there are some issues with PDFs people have purchased previously not being available, but WotC are stating that they intend to release the remaining PDFs "in waves"... time will tell if they hold to their promises!