Discovered 2hash yesterday – a simple GPL’ed tool to calculate the md5 and sha1 hashes of a file in a single read. If you’re regularly checking/calculating hashes of large files this’ll save you a lot of disk IO.
Update: The source site is down, so I have mirrored it here.
Update 2007/10/26: 2hash, by default, doesn’t support large files. If you compile it with the CFLAGS updated with ‘-D_FILE_OFFSET_BITS=64’ (as recommended by this page), it will work.