See the Choosing a Client page from the Ethereum Documentation.There are numerous clients (Go, C++, Rust, Python, Java, Ruby, Haskell, JS), with fork support now having hit:
And the Mist browser and wallet:
Whatever your preference, please do update your client, to ensure that we get a clean network split, even for geth clients using fast-sync and light client protocols.I note that the EthereumClassic client has also branched from geth-1.4.10, but with the defaults changed. Good job!