This Bitcoin Script IDE might be useful, but there might be a bug in it.
http://www.cs.princeton.edu/~tongbinw/bitcoinIDE/build/editor.htmlThe following thread discusses signing transactions on the testnet, and using the IDE to track down problems, but one of the final comments says it was giving inconsistent results with known good values. However, the IDE might have been updated since then.
Last time I checked, it is still buggy. This one
https://webbtc.com/script is one of the best so far, despite it does not work lately.