Best option for getting teeth whitened?

Hi all I woke up one morning to find my teeth are a bit discolored and must find out the best option for getting em whitened. Are there do it yourself type kits available locally? Must one go to the dentist? Anyone have some experiences here to share about whitening processes done at dentist?
Obviously not going to the dentist and finding something sold locally that whitens teeth would be best but if i must then off to the dentist i go. Those eight cups of coffee a day are starting to take a toll on my teeth.