Here is another recommendation for a subscription to
Dungeon. It has been the best accessory for my DMing for the past 10 years--the best money I've spent on gaming aside from the core books for the last 3 editions. I have and could still run endless campaigns with just the magazines and the core books. I
hated getting rid of about 40 old AD&D issues last month, but I'm not going back to AD&D and I feel like I ran all the adventures that I thought were the best ones. You might even pick up the 3 most recent issues to get 3 parts of a very cool poster map of Greyhawk as well as a nice-looking mid-to-high level adventure trilogy (part of the 3 adventures in the magazine every month). If you're really feeling bold, go to
www.paizo.com and get the Dungeon Shackled City adventure path. It spans 11 issues. Spend your money on Dungeon and it will have been spent wisely (but you might want to check with the other DMs to make sure they aren't using it already).
An adventure & campaign setting that I picked up recently and really like is Mesopotamia. It's full title is Ancient Kingdoms: Mesopotamia. Necromancer Games publishes it. It is a nice adventure with some light setting information. I wouldn't use all the setting stuff (I don't use prestige classes, nor do I want a different magic system), but the adventure is all good.
Otherwise, judging from the books you have, my advice is to pick the setting you like best and start buying published adventures for it. If a setting doesn't have any modules, then the campaign is probably not worth the investment of your time & effort. If you're a player in a setting, then you might want to stay away from adventures in that setting. Eberron will probably be supported at least for a while, although I know little about it and even less about the others you list.
I'm also saving some of my future gaming purchasing dollars for The Horned God Complete Campaign from Mongoose Publishing. It is a conversion to 3.5 D&D of 4 modules from their Slaine d20 line. I think it could be a very good module for a celtic game. It's not due until April, though.
Those are the best picks I can give you today.