New maintainer for swfmill
The swfmill project converts between a special dialect of XML and SWF files. As well as being used by many people for linking together existing SWF resources, it also happens to be useful for changing SWF files at the lowest possible level, giving access to every single property and element of the bytecode.
The last release of swfmill was over two years ago, and since then it has gained basic support for ABC tags - the bytecode for ActionScript 3.0. This is crucial for Gnash's fledgling AVM2 support because you can directly edit the ABC opcodes to see what the effect is, as well as adding regression tests for all sorts of weird cases. Because the project has stagnated for so long, these new features aren't yet available unless you build swfmill yourself.
The good news is that a new maintainer, Daniel Cassidy, has volunteered to take over, so swfmill can finally get another release, this time with ABC support. I hope we can expect a release in the next couple of months.