Safari 6 keeps suddenly crashing on Lion
A common reason for an application crash is a corrupt preference file. The first thing you'll want to try is backing up and deleting your preference file for Safari.

Close Safari, and then you can find the preference file by going to ~/Library/Preferences and looking for the file called com.apple.Safari.plist. Once you've found the file, back it up by adding a tilde to the front of the file name so it becomes ~com.apple.Safari.plist. Once you restart Safari, it will generate a new .plist file.

If that doesn't work, the next step would be to do a permissions repair using Disk Utility, which you can find in /Applications/Utilities.