|Color Scheme Designer|
Paper samples available for free at DIY such as the Home Depot (for paint) was the first 'tool' that I used to find which combos I liked most. It was pretty useful for my home: the colors weren't too bright and I had quite some fun with it. Their clever online tool, Behr's Color Smart Tool is really very nice for choosing colors for your house. You can even paint your own house virtually!
I haven't found a software available for free, but I've come along a few nice color generators though:
Seeds offers an amazing amount of incredibly beautiful pictures and color palettes which you can download for free and print. There is something for everyone's taste; if you are stuck and need inspiration, this is the place to go. No need to go further if you don't have your own image.
Bighugelabs , focused on fabric, is also a nice color generator using your own picture - the result is quite exhaustive - many beautiful colors... See here what JaneVille's design look like thanks to this tool. It allows you to download the swatches in Adobe Swatch Exchange (ASE) format for Photoshop or compatible applications and CSS Drive (yes another one) allows you to save the palette as CSS stylesheet (.css file) or photoshop swatches (.aco file).
There are many color palette generators online, but I think that my two favorites are Seeds for the inspiration by color and by theme and Degraeve (white background) and Color Hunter (dark back-ground) for their succinct selection of the colors.