i have never understood the need to be told a good colour to go with one you currently have. surely you think ok i want to make a site with green, what looks good with this shade, try different shaeds of blue, red, brown etc, see if it works, choose one, then repeat for other sections.
I make websites for a living and 99% of the time use my own judgment on colours, but sometimes a little help can provide a bit more inspiration. It's just when you are churning out 5 different mockups for a client who doesn't have a corporate colour scheme its good to have a bit of variety.