Deleting Categories

Does anyone have any tips on deleting categories? I recently imported my old blog into WP and it had over 550 categories–which were all technorati tags on the old blog. . . Now I have a nightmare to manage. I already use a tagging plugin to get technorati tags in my posts, so I want to reduce the number of my categories down to about 10.

For now I have been setting a default category which matches a range of those I need to delete and then one-by-one am deleting them. It is slow, especially with the scripting bug in 2.0.5 which causes a hang after about 4 deletes.

Any suggestions?