I've deleted about 100 posts from my wordpress blog. All of these pages were indexed in Google. To prevent any negative SEO, is there something I should be doing or just let it run it's course until Google removes them from the index. Right now, all the pages just go to a 404 page not found message.
You've already done it. What ever you could have done (which is probably nothing anyway) is too late. Why would you delete them anyway, just curious ? Just update your permalinks, and you could also redirect your 404 page to go directly to your home page (or customize it).....that's about it as far as I know.