Half Life 2:Deep Down is my new project and its more than well underway. I have one map complete with 3-4 maps to go.
A ModDB page is up here: http://www.moddb.com/mods/half-life-2-deep-down
Take what I learnt building Daylight and expand on that to create a full HL2 mini episode. The mod will feature a fully functioning Alyx, a fully functioning Vortigon with custom voice, driving sections and some new NPCs (I hope!).
It will also feature locations from Episode 2 such as White Forest base.
Modding for Episode 2 is tough because you have no access to the code base. So anything new must be created via entities in hammer.
For example, I want a new NPC that uses a grav gun to pick up prop_physics entities and throws them at the player. Via code this may be reasonably simple to achieve, by finding entities that act in a similar manner (zombs hit prop physics objects at the player). But through entities, these kinds of behaviors can be very difficult to achieve.
It's always the way with my work, the more I play test, the more the content of my mod grows.
To keep this under control I've given myself a deadline of End Of July 2012 to release.
As a result I need to cull many of the less than great ideas I've had so far.
Anyway, please drop by the Mod DB page and take a look.