Are you looking to use published adventures, or do you have the time and inclination to work up stuff for yourself? (Or somewhere along the spectrum between. I, for example, have extensively used published stuff for my Eberron game, but as it heads toward an ending, I'm finding myself creating most of it.)
Are you going to use a home-brew world, or a published setting? If the former, is it "default D&D" in tone, or something a little different? If the latter, which one do you have in mind?
Or you could use the old downloadable adventures from WotC. It's a little tricky to navigate the website to get to the "old" 3.5 section, but they're all set up for you. I'll be honest - I've never run one of these adventures, but I have them and I've browsed them and they look pretty good.
Here's where to go: Original Adventures
Personally, I also like the look of this one (not on the list, I think it was in a magazine feature...), which I am attaching. 1st-level PC side trek.
For my first time around I am probably going to want something published, just so i can get a feel for how to run things. I have some ideas of my own, but they need to be developed further before I even consider using them in a game.