Is there an event viewer type application in OS X?

Basically my computer keeps having "you must restart your computer" errors and I don't know what's causing the problem right now. Is there anything in OS X that is basically like the event viewer functionality in the manage computer pages in Windows? There must be a log somewhere of what went wrong because OS X keeps sending off error reports to Apple.

Got it. I'll keep an eye on it the next time it happens. Am I right in assuming that there's a memory checker on the applecare disks? I swear I heard about it before.