Several sites beat Monday's planned introduction by GM by releasing sets of photos today.
Autoweek has an overview here, with full details after next Monday afternoon: http://www.autoweek.com/apps/pbcs.dll/article?AID=/20080718/FREE/261484376/1528/newsletter01
However - as usual - the folks at Camaro5.com have the full set of photos: http://www.camaro5.com/forums/showthread.php?t=5171 and the specs of the first two engines that will be be offered: a standard 300-HP 3.6 V-6 and a 400 (automatic)/422(manual)-HP 6.2 V-8. The V-8 model weighs 3800 (dependent on options and transmissions) pounds and has a 52/48 weight balance. Furthermore, the base V-8 has variable cylinder shut-off and with a standard 6-speed transmission will have extraordinarily low revs at highway cruising speeds. Like the Corvette with the similar engine and transmission, careful drivers will find high-20s on the highway.
Both V-8 and V-6 models "blow away" the Mustang by a considerable margin. And rumor has it that the 2010 Mustang coming next spring will use the existing engines. If so, that's bad news to Ford.


Production doesn't begin until next February. Full specs and further official photos will be revealed Monday afternoon by GM.
Reference- Challenger vs Camaro vs Mustang: http://www.challenger.drivingenthusiast.net/sec-competition/index.htm