Is quite simple to do in bitcoinj. Do you have a format in mind? If so send me an sample will see what I can do. Please DOUBLE check it is signed correctly! Make it a transaction that sends to my address below and I will have more motivation!
I was thinking that if
www.bitaddress.org could also create/sign transactions (not trival as need to link all the inputs), then if you had this web site you could then create transaction totally offline.
It might not be a good idea to construct the transactions online, because that means you're giving your private key to a 3rd party (and sending it over the wire).
Yes, it looks like the domain is not online anymore. In any case, I'm working on getting a page up that will do this.