Magic Matching Color is an application for Windows that will help you out in this department, since its mission is to assign colors that will form a perfect palette for your site. That way, not only do you not have to worry about choosing your own colors, but you can also find out which are the most suitable for your overall design.
To use it, just select a color - presumably the main color of your website, or the one featured in your logo. That's all you have to do; the program will then display the other colors that mix best with your original. After that, just copy the color codes so you can use them.
All of this makes Magic Matching Color an interesting tool that's well worth the download.