It is likely that you have an incompatible plug-in (such as an input manager) or contextual menu item installed. Do the following:
a) Log out of your account then log back in while holding down the shift key - this will do two things:
1. it will disable all third party extensions and fonts and your login items, and
2. it will clear a number of caches to the trash.
b) Navigate to ~/Library/Contextual Menu Items (or /Library/Contextual Menu Items if that is where they are installed) and move the contents out of the folder to e.g. a temporary folder on the desktop. Do the same for the contents of the ~/Library/Input Managers and /Library/Input Managers folders. Fwiw, the most likely culprit for this behaviour is Stuffit Expander's contextual menu item, so if you want to do it in a step-by-step fashion, try removing this first, upgrade to the latest version of Stuffit Expander and choose not to install the plug-in.
c) Once removed, log out and back in again and the Finder shouldn't crash any more. If it still does, the next potential culprits are Quicktime plug-ins such as DivX. Remove and upgrade them to their latest versions in a similar fashion.