CyanogenMod 6 RC1 for Nexus One is out. Edit – Includes all red screen battery saver mode!
And the new Homescreen Tips are awesome 
Find it HERE.
Edit – Just noticed this in CyanogenMod Settings, there’s a “Render Effect” setting that allows you to do this to greatly increase battery life:
As detailed on Engadget in THIS ARTICLE.
Obviously not something you would leave on all the time, but if you’re away from a charger (and won’t be near one for a few hours), and you’re down to 30%, it could be a real life saver. Great stuff from CyanogenMod as usual.
Edit 2 – Just tested the battery saver red screen mode. I just enabled screebl to keep the screen on, propped the phone up on my laptop, and swiped down, then up to unhide, then hide the notification bar every 5 minutes to keep screebl’s fail safe from turning the screen off.
I charged my phone fully, then started the test, and the stopwatch, and stopped when the battery level reached 90%.
In full color mode:
I then hooked my phone to the charger and fully charged again. I put it in red screen mode, unplugged it, and started the clock again, also hiding/unhiding the bar every 5 minutes.
I’m sold. I’ll keep it in mind when I need to stretch my battery life.