Cryptographers -- List of peoples' home-pages
PGPi -- The standard encryption program for Windows
Cryptogram -- Top reccommended monthly magazine
KMail -- Email client for GNU which supports encryption
EnigMail -- Encryption plug-in for MozillaMail
SecureBat -- Excellent secure email program for Windows
Google -- Other hard-disk encryption programs
PGPPhone -- Strongly encrypted phone calls over the internet
SnakeOil -- Bruce Schneier's great article on evaluating crypto-systems
GPG -- The GNU privacy guard (linux)
PGPDisk -- Protect your hard-disk (Windows)
Evaluating -- Evaluating encrytion software
More so than with any other type of software, be very wary of anyone offering encryption. Closed-source and commercial software is simply not suitable for encryption -- see the links on evaluating crypto programs.
Nearly all programs now use the PGP standard, with algorithms that have been analysed in the public-domain for decades before being accepted by the community. If someone comes up with their own 'new' form of encryption, don't trust it. Open algorithms are the only ones which have been examined carefully enough to be used
For anyone who still wants to trust a commercial product, have a look at elcomsoft who sell programs which can crack the encryption on MS-Money, MS-Word, WinZip, etc. in seconds. Still trust microsoft with your data?
PGP is standard. GPG is the free implementation of it.