I recommend the Sunless Citadel; its unabashedly a dungeon crawl which is designed to highlight some of the basic 3E rules. Its straightforward to DM and its a lot of fun. If you want to get creative, theres also some room to expand the politics and RP interaction.
I'm also enjoying the Freeport series, though they require a lot more DM work. They arent quite full-sized adventures, so you need to provide some padding, and they are much more RP and investigation intensive which leads to more DM work. (Ask yourself this -- if your players found a "to-do list" with the word "turnips" buried beneath several more promising clues, would they immediately run to the local open-air market and begin investigating all of the stalls selling turnips? If so, Freeport is going to be a lot of work for you as a DM.) If you run Freeport, I also highly suggest you read Dr. Nuncheons original story hour. Its great as a playtest walkthrough, its got some good ideas of how you might frame the adventure, and its fun to read. All good.