Well if you look to the left of every post you make, you will see the current number of posts you have made. As far as viewing previous posts, all you can do is just browse through the boards to see what you have posted in the past. It would be cool if there was a list of every post a person has made on thier account page. Problem is that once you reach a few hundered posts, it would get pretty crowded there. There is a spot for last 10 posts there, but it doesn´t seem to work.
if you click the FORUMS link in the left menu, then scroll all the way to the bottom, there is a search box. but next to that is a link to ADVANCES SEARCH. click that and then you can search by author. here is a direct link to the advanced search.