Spoiler
Download: http://sourcemm.net/downloads/
New Engine Support
Support has been added for using Metamod:Source on Dota 2 on Windows. Note that only the gameinfo loading method is supported as Dota 2 does not have support for VSP plugins.
SDK Changes
AlliedModders has reverse engineered a Dota 2 SDK capable of building plugins. It is still changing often as the game itself changes internally, but it is enough to get something as large as SourceMod working on Windows. You can grab a copy from our Mercurial forest (see the bottom of the page). If you discover any changes yourself, we greatly appreciate bug reports or any attempts at notifying us.
New API Changes
Metamod:Source now treats Team Fortress 2, Day of Defeat: Source, and Half-Life 2: Deathmatch as separate engines, since compatibility between them diverges as they now receive game updates at different times. Additionally, Nuclear Dawn is also now separate from Left 4 Dead 2 for the same reason. GetSourceEngineBuild now returns new values for each except L4D2. Similarly, users of the "extended loading" API will see the new values in MetamodVersionInfo.
Full changelog
Added support for Dota 2 (Windows only for now).
Split TF2, DoD:S, HL2:DM, and ND to separate binaries (bug 5667).
Updated for latest games changes on HL2:DM, TF2, CS:S, DoD:S, L4D2, and Dota 2.
Added basic VDF file for easier installation (bug 5681).
Removed loader's reliance on tier0 by manually parsing command line for -game (bug 5674).
Fixed MetamodVersionInfo::GetGameDir always returning NULL or garbage.
Added META_NO_HL2SDK define to stop MM:S headers using the HL2SDK (bug 5079, bug 5469).
Remove unused variables and defines (bug 5523).
Fixed NULL conversion compile warning in loader.