Our developers tend to use the Crypto provided with .NET and do it in the application, but there are some options from 3rd party vendors. Here are some:
NetLib Encryptionizer for SQL Server
XP_Crypt
Application Security Inc. makes dbEncrypt, but not sure what happened to them. There's a press release from Dec 2003 but right now a whois on their domain (appsecinc.com) returns nothing.
K. Brian Kelley
@kbriankelley