Bitcore and BitcoinJS achieve a lot of the same basic functions like generating addresses (and now multi-signature addresses), building, and signing transctions. You will still need to be able to connect to a Bitcoind peer (via an API or run your own) to promulgate the transaction on the Bitcoin network. http://cryptocoinjs.com/ is another library that performs some of these functions. Rubyists may be interested in https://github.com/lian/bitcoin-ruby