Quake Arena requires Flash Player 10

Cocomo is

"a Platform as a Service that allows Flex developers to easily add real-time social capabilities into their RIA"

Alchemy is

"a research project that allows users to compile C and C++ code that is targeted to run on the open source ActionScript Virtual Machine (AVM2)"

So you see, soon enough you'll be able to play Quake Arena online in your browser :)

[Update]
Load up your chain guns!
It's on /.
:D