These consist of the earlier spoken about Whirligig and also a re-re-make of Hoshi.
Whirligig I've not worked on since the tech demo, except to do some testing. I can confirm it works with more than 2 players, but it is the bigger of these two projects so, despite starting it first it will take longer. Also I used it as the test bed for a lot of the framework I'm developing for use in my game-a-month project and I spent over a week getting this working to a satisfactory and easily reusable standard. However, when I started work on Hoshi, this meant I could just drop in a lot of this framework with very little change and now I have two games where I just had one two days ago. Perhaps I'll release some of this framework afterwards, we'll see.
A little more on Hoshi here: when I first found OpenTK one of the first things I wrote for it was a re-write of my uni game Hoshi. Again I got around 75% of the development and then discovered I'd made a huge (and I mean huge) error with how I was translating all the objects around the screen. Untangling this mess would have taken as long again as a total rewrite, so I essentially left it there. There are some videos of the engine on youtube. So, I'm once again re-making the game I put so many hours into as a kid. Right now I have a starry sky (just a quick note, the word hoshi in Japanese -- kanji 星 -- means 'star') and a ship that can fly around it. I have ship designs for the enemy ships in place and I haven't mucked up the positioning system yet. I'd say I'm around 70% of the way to a tech demo with it and around 50% of the way to a full game.
So, those are my current two dates. Hoshi I estimate will be ready sometime in May, I'm going to say provisionally the 16th, since it's my birthday and this was one of my favourite games. ;o)
Whirligig will take longer as I've more plans for it, mid to late June is probably a fair estimate.