The Toolkit includes DEdit (world editor), ModelEdit (modelling editor), LithRez (program for (un)packing AVP2), SoftImage 3.7 exporters, Maya and 3D Studios Max exporters, sample map files and is chock-full of documention and a list of online resources. All that for just 8.5mb! The update includes a new dynamic lighting tutorial and changes to the map and model files. They also contain additional documentation.

Aliens vs Preditors 2 released their mod tools for the game. Maps and mods can now be more easily made. You can find the download on FilePlanet.

I suppose I should leave a link to this in the downloads section as well.