Alright.Lets start with the first Opposing Force.As I know theres around 4 or 5 remakes,and as far as I know,no progress is being made now.I think they've died pretty much.Correct me if I'm wrong.
I've seen one.Just thought I'd create this topic becuase sure these mods will probaly never see the light of day but maybe some people who fancy doing a remake of this game could learn from what was being done.
http://operationblackmesa.vossey.net/models.php
I couldnt find anything else despite googling it,this was the first thing that came up.Everything else wasnt concerned with the mods being made with the source engine.

Now,there actually is a sequel,of sorts.Yep it's another mod,but from what I've seen it looks really promising.As good as Black Mesa source will be?
http://www.moddb.com/mods/10775/opposing-force-2
Problem is it's still being developed.Think its around at 10/20%.Wouldnt expect it to come out till at least late 2009.