BABloggee Dan Fischer emailed me to say that comet 17P/Holmes has brightened incredibly, from magnitude 17 to magnitude 3 literally overnight. That's a brightening of a factor of 400,000!
I will go out and check this tonight for sure! To see for yourself, first, be in the northern hemisphere. :-) Then around 8:00 local time face northeast. See the big W on its side, facing left? That's Cassiopeia. Below is the star Mirfak (if you keep looking lower, near the horizon, you'll see the far brighter yellow star Capella). The comet is just below and to the left of Mirfak, and the star is about 3 or 4 times brighter than the comet is supposed to be -- unless the comet gets even brighter or fades away. The comet should be easily visible and fuzzy-looking in binoculars.
Sometimes comets can brighten a lot if they break up a bit when they are near the Sun, exposing previously buried reservoirs of ice which then sublimate and are lit up by the Sun. If this is what happened, we need as many observations of it as possible to nail down the brightness. Given that Comet Holmes is over 220 million miles from the Sun and 150 million miles from the Earth, this is very impressive indeed.
If you get pictures, post them on BAUT!