Sounds like your throttle body needs cleaning.
Its best to remove it but it can be cleaned on the car, just use some carb cleaner and a cheapo tooth brush to scrub away all the deposits in and around the throttle blade. The idle air bypass solenoid could be sticking too. Just take the hose off that feeds it and spray it liberally with some wd-40 and they usually free up nicely. Also if you run regular unleaded all the time its a good idea to run a bottle of fuel injector cleaner when you fill up at least once a month and I'm not talking about that cheap $1 dollar a bottle either, spring for the good stuff.
Hope this helps, Charles