The largest concentration of 1E players on the net seems to be at dragonsfoot.org. In general, ENWorld is more openminded about prior editions than Dragonsfoot is about 3E, but people still let their personal preferences be known here...and generally they're of the "why 3E is so much better for me than oD&D, 1E and 2E" sort...but not all of us fall into this camp.
As a matter of fact, Dragonsfoot is very open to 3rd editioners! Just stay away from the "Edition Wars & RPG Soapbox" forum. We have a forum expressly for gamers who want to discuss the latest incarnation to bear the name D&D and I personally boot anyone out who flames in that forum, don't I Ermanaric?
Additionally, I am the editor of the soon-to-be created "Everything Else D&D" section on the site. This section will be devoted to all D&D that's not 1e. So far, I have revised rules on 3e multiclassing, a 3e "True Illusionist" and have been promised a 3e module.
We also have forums dedicated to Hackmaster, Lejendary Adventures (moderated by Col. Pladoh himself) and CoC along with a forum called "Other RPGs". So, you see, even though Dragonsfoot is dedicated to OAD&D, we're a very gamer-friendly site. Come visit us sometime (just stay away from the Soapbox!).