N.D.
My tot does this every few months where she becomes a bedtime banshee.
Two year olds are testing their limits, and their boundaries. You need to show who is the boss and what she can and cannot do. You can let some things slide, like we all do, but bedtime needs to be handled in a very consistent and firm manner.
As of note: She still is in her crib, so doesn't have a bed. However, I DO agree with Supernanny's methods, and plan to do that when she goes to a toddler bed.
What works for us is we firmly tell her goodnight and shut the door. She squeals and cries and begs for one more Elmo song, one more glass of juice, etc, but we just say "no, it's night-night time." Period.
She will squeal for us to come back, cry, show us her saddest face, but after we leave, she realizes that her little charade for attention is not going to work. It's hard for us to hear her pleading, but we know as parents it's what's best for her. And each evening becomes easier and easier as long as we are firm and consistent.
Then bedtime becomes easy again, going to sleep peacefuly for 12-14 hrs at night...until she tests her limits again a few months later.
good luck!