Two new rear lights, which I haven't seen mentioned here (probably because the thread died out 12 months ago!):
(i)
Exposure Lights - Flare, which is powered by a CR123A disposable, or RC123A rechargeable. Exposure quotes 75 lumens output, which is pretty damned bright.
(ii)
Light & Motion Vis 180, which is powered by an internal Li-Ion cell, and seems to require a micro-USB connection to charge it up (as far as I can see no charger is supplied, but I could be wrong). It's quoted as having an output of 35 lumens, which is still quote bright.
The Flare seems to be primarily intended to be fitted to seat-posts, whereas the Vis 180 looks like it's mainly meant to be fitted to seat-stays (and other relatively thin tubing), although possibly seat posts can be used as well (it's hard to say without actually looking at it).
The Vis 180 interestingly has side amber lights, whereas the Flare only seems to scatter some of it's single P4 emitter off to the sides.
If you've got the 10% discount at ChainReaction currently (which a lot of people have for the next few days), then the Flare is £36 from them (disposable battery option), and the Vis 180 would be £81.
I haven't seen either of these yet, but they look interesting (although probably not for group rides).