Adwords has a new enhanced keyword tool:

Similar to previous tools you have the standard option to enter keywords and generate further related keywords (with some poor degrees of relevancy)

But it can also take into account adgroup history and display the top performing keywords, giving you the option to generate from these keyphrases only, a good optimisation function.

However the best function in our opinion is the ability to search from a site url, the content related keywords we found were relevant and very useful to the campaign.