• Microsoft Encrypt available in right click properties.
• Bundled encryption software such as Acer e-Protect.
• Commercial file encryption software. There are dozens of choices. I have no experience with them. Keep in mind none of them will stop the IRS, FBI, CIA, KGB, Mosad etc. These are designed to stop individual snoops.

• XORing with a key phrase. This is relatively trivial to crack, but keeps out casual prying eyes.
• DES. This is fast, but can be easily cracked by all US government agencies.
• RSA. 40-bit can be fairly easily cracked. 1024-bit or higher would require secret special-purpose hardware that presumably the CIA has. The Transporter supports up to 4096 bit enryption, but is suitable only for short messages because it is so slow at decrypting.
• One time pad. This is in theory uncrackable, but has the problem of needing to distribute one-use-only keys just as large as the messages ahead of time. I have written a Pascal implementation. If you are working at this level of security, you must write your own program to be sure it contains no trojans.
• JCE supports a number of different algorithms from 40 to 2048 bits. The more bits, the more secure, but the more CPU time needed to encryt and decrypt. You use the generic javax.crypto.Cipher class both to encrypt and decrypt the the message. You use the javax.crypto.KeyGenerator class to generate random numbers to use as keys.
• AES: Advanced Encryption Standard as specified by NIST in a draft FIPS. Based on the Rijndael algorithm by Joan Daemen and Vincent Rijmen, AES is a 128-bit block cipher supporting keys of 128, 192, and 256 bits.
• Blowfish: 56 bits. The block cipher designed by Bruce Schneier.
• DES: 56 bits. The Digital Encryption Standard as described in FIPS PUB 46-2.
• DESede: 112 bits. Triple DES Encryption (DES-EDE).
• PBE: Password Based Encryption algorithm (defined as part of the PKCS #5 standard), defines how some other alogrithm can get its its key. It derives the encryption key from a passphrase. It is not an enryption algorithm on its own.
• RC2, RC4, and RC5: Variable-key-size (32 .. 160 bit) encryption algorithms developed by Ron Rivest for RSA Data Security, Inc.
• RSA: The RSA encryption algorithm as defined in PKCS #1. Public/private key.
• HMAC-MD5, HMAC-SHA1 : 64 bits.
• Diffie-Hellman : 1024 bits.

For email signing and encryption, the two most common schemes are PGP often used with Eudora, and smime often used with MS Outlook.