I have recently been experimenting with the cryptopals crypto challenges, and have found them very interesting. Below are my solutions to set 1, which I will be expanding as I go. Please play around with them.
1) Convert a Hex string to Base64.
2) Calculate fixed XOR of two Hex strings of identical length.
3) Decrypt Hex encoded string which has been encrypted with single byte XOR cipher.
5) Encrypt message with Repeating-Key XOR Cipher.