I've run into this more than a few times over the past couple months.
Check your ~/Library/Safari folder. That is, the Safari folder in the Library folder in your Home folder. More likely than not there is something corrupt in there.
The easiest thing to do is to move the contents of your ~/Library/Safari folder into a temporary folder then launch Safari (this allows you to clear out the folder while retaining a backup). If Safari launches successfully without crashing, quit Safari and restore your Bookmarks.plist file to your ~/Library/Safari folder (this will restore your Safari bookmarks).
Good luck. I hope this does the trick for you.
James