Can anyone give me a good site to find out price values on vintage bicycles?

I bought this Kent Gran Sprint road bike at a flee market for around June/July.

http://i198.photobucket.com/albums/aa212/MAH_029/DSC_00042-1-1.jpg

I’ve looked all over online but I never found an official site for Kent bikes or on other sites such as Ebay, Amazon, bike forums, etc.

I wont check the local shop in town cause they’ve always been rude to me and other customers and just like to give people crap/rip them off if they have low knowledge on bikes.

Any kind of help will be appreciated.

I added the extra stickers and such to it so it fits my personal taste.
I don’t plan on selling it, but more of upgrading it once I find a job.