This is small tool capable of calculating CRC-16, CRC-32, MD-5, RIPE-160, SHA-1 and other variants.
It can be added to context menu for all files (SHA-1 is added by default).
There is also command-line interface available.
Program requires .NET framework 2.0 (or higher).
However, if you do find it useful, I wouldn't say no to a small donation.