I have just pushed a simple class called SimpleCrypt to GitHub:

https://github.com/glenscott/simple-crypt

This is an OO wrapper around the most common mcrypt functions. An example of use:

require_once 'SimpleCrypt.php';

// show the algorithms available for use
print_r( SimpleCrypt::get_available_algorithms() );

// encrypt a string using Triple DES (CBC mode)
$crypt = new SimpleCrypt( 'tripledes', 'mysecretkey' );
$encrypted_data = $crypt->encrypt_data( 'stringtoencrypt' );
echo "Encrypted data: " . bin2hex( $encrypted_data ) . "\n";
echo "Decrypted data: " . $crypt->decrypt_data( $encrypted_data ) . "\n";

If you find it useful, please let me know!