This was probably showed on the BB in the past, but I just used it, and it is so neat and easy, I give the URL here:
HTTP://POSTCALC.USPS.GOV/

It is the post office's postage calculator. Bookmark it.

For example, if you have a 2 pound package going from Brooklyn (11201) to Connecticut (06812), it comes to $2.97 for parcel post, which is about $1 less than Priority Mail.

Try it. (1) Click the above link, then (2) click "a package", then (3) put in 11201, 06812 and 2 in the proper boxes and click "continue," and there it is -- $2.97

Robt.