Indeed, it is really useful . The IETF working groups are developing them, so it's no wonder we would use RFCs as sources for info on protocols.. . Anyway, unless you have the RFC number, a nice place to visit is http://www.rfc-editor.org/rfcsearch.html . "Oh, RFC 2616.. is it HTTP 1.1?". Heh, we don't need to run into that kind of trouble..
And when you have the RFC number, another way of retrieving them (I like multiple choices), extracted from the rfc page at ietf:
Alternatively, if you do not have Javascript enabled you can type the following in the location field of your browser:

http://www.ietf.org/rfc/rfcNNNN.txt

where NNNN is the RFC number prefixed with zeroes as necessary to make a four digit number.
And for those who wonder what is IETF, IESG, ISOC, IANA, RFC, FYI, BCP, STD, etc, a good reference is www.ietf.org/tao