Google Sets allows you to generate a list of similar terms by just typing a few keywords; it can be a great little tool for generating new keyword ideas to explore and expanding on your existing keyword lists.
How To use Google Sets
Sets used to be a Google Labs experiment which was discontinued; the good news is that you can access it via Google Drive.
Log into Google Drive and open up a new spreadsheet, type in a few terms, select them and then hold down the CTRL key whilst dragging the corner handle of the selected area down.
How have you used Google Sets?