For battlefield control, look mostly at the Conjuration spells.
Grease and Glitterdust are a great start. Depending on your group, the Summon Monster line could be good for extra cannon fodder/flankers. As an added bonus, Spell Focus: Conjuration works to both boost your save DCs and as a prerequisite for Augment Summoning.
You're going to want Mage Armor eventually. I like chuffster's recommendations for more control spells. I'd add Obscuring Mist, and stuff like Stinking Cloud, Sleet Storm, Aqueous Orb, and Black Tentacles when you reach higher levels.
Again, depending on your group, Haste could be the most powerful spell in the game once you can take 3rd level spells. If you've got 3 or more weapon focused damage dealers, you just gave them an extra attack per round at max BAB. If your party doesn't have that many weapon guys, then maybe stick to fireball first, for some extra direct damage.