I agree with Alex that it probably is just a phase that she'll grow out of fairly quickly but I'm sure it's not much fun for you!
Do you still have a good bedtime routine in place though? It can really help if you follow the same routine every night - maybe with food, a bath, gradual dimming of the lights etc ... all to show that bedtime is coming. Also, make sure you're being 'boring' with her in the half hour or hour prior to bedtime. In other words, if you're being fun with her, bouncing her around and keeping her excited then it will undoubtably take longer for her to calm down and drop off. Be boring!
Chris