...blue berry? The flower is white with a blue hue. it has 5 petals, and is star shaped. it is a vine type plant,and I noticed some small thorns on it. The dark blue berry has several seeds inside.
I live in upstate New York
Also, the seeds are in one clump inside the berry

Sounds like it might be blackberry. They do not grow as a bush but as a vine. Not knowing what part of the country you are in, really can't say for sure. If you are in the Texas, Arkansas, etc. area, they are quite common. Very good to make jam, jelly, cobblers and I have known people who canned them. If they are blackberries, be sure and make a cobbler and top it with ice cream. It is delicious.

could it be one of the deadly nightshades?...

http://images.google.com/images?q=nightshade&svnum=10&um=1&hl=en&rls=com.mi crosoft:en-us&start=20&sa=N&ndsp=20

the first page has mostly the purple ones, the second page, the white ones....
nasty stuff... yank it and toss it....NOT in the compost tho....