The 3.5 Player's Handbook and Monster Manual are now available at dndclassics.com.
Up until today, none of the material WOTC reprinted, like the core rulebooks for 1st-3rd editions, Unearthed Arcana, or the A and S series of modules, was available in PDF. Looks like that's changing. Here's hoping we see PDFs of the 1e PHB, MM and DMG.