This tool will allow you to either encode / encrypt a string to its MD5 hash. You can also perform the same operation for SHA1 hashes, and convert to and from URL encoded strings, Base64 and Base85 ( aka ascii85). Also added is MD4 encoding, but not decoding.
Note: Any data which is MD5 hashed is stored for lookups. Do not encode sensitive data using this form. If you are storing MD5 hashing in your databases, it is always advised to salt your hash first.