I've been running a Forgotten Realms campaign since last May or so, and I managed to get going in a pretty simple way. I nabbed the Cliffhanger adventure "Unearthing the Past" from the WotC website and made a few modifications. Mostly I changed the evil cleric's god to an FR equivalent.
I'm running a lot of differences to the campaign from what's in most of the sourcebooks. Namely, I began the campaign in Hill's Edge -- though it's a modified Hill's Edge that's only a village of 200-some people instead of a city of 10,000+. The players followed the basics of the Cliffhanger adventure for a few sessions, killing the orcs and one of the brothers. The other escaped and joined up with some Zhent supporters. Meanwhile the players explored the dwarven ruins set in the Sunset Peaks. I expanded the dungeons, and gave them a bit of simple non-combat-oriented magic to get them started.
I free-form play, mostly, so I went off of what my players were doing and discussing with each other. They tend to role-play a reasonable amount, and a lot of moral situations and minor party squabbles come out of it, lending me with more ideas.
Anyway, after solving (for the most part) the Cliffhanger adventure, and seeing that they still needed some time to generate a few ideas for me, I decided to use one of my favorite adventures from an old D&D supplement, AC10, Bestiary of Dragons and Giants, in which a red dragon, polymorphed into human form, takes control of a town -- in this case, Hill's Edge. Given the original level of the adventure, I was able to use this to get the players out of town for awhile so they could gain more knowledge about their enemy while gaining some levels.
They recently returned and slew the dragon and have begun reconstruction of the town.
Is some of this corny? Sure. Has it kept them occupied for 9 months? Yes.
My point is, check what you already have. You might be able to convert something to use in your game, and it could turn out to be really fun. I've gotta say that one of the most interesting things in my game is that I've had a player with a priest of Tyr who just happens to be racist (in this case, against elves -- "They have no respect for the Law!"). It's made for some hilarious role-playing, and some really tough situations. Most notably, the recent meeting between the player's character and an elf who also happens to be a priest of Tyr.
I've been very happy with the simple conversions of some "one-session" type games into something that's lasted for the better part of a year. Now, I'm looking for something new along these same lines to throw at them, and I'm pretty sure something will come up soon!
Good luck! I hope this helps!