Wordpress Forum or Other?

I’m looking for a forum/answers script that does something very simple. All I want is the ability to have a post form with sign up information on the same page and two category choices, e.g. category and tag list dropdown. This way a visitor can post immediately and identify a category and special tag without requiring them to first obtain a confirmation and then post. Ideally I’d like them to confirm their email as a way to validate the post.

I’ve seen a wordpress theme do something like this and almost be a cross between wordpress and vanilla, with the category using the site’s category list and a separate tag field that I’d rather just display as a dropdown from a list of prepopulated tags. Has anyone done something like this? What have you used?

Some of the issues have been that it becomes very difficult to search through forums/categories for answers and there is no good “advanced search” for wordpress that allows you to easily sift through categories and tags and perform that drill-down simultaneously. Perhaps there is one.

A follow up - I’d also like to have guest posting, sort of the way comments work in wordpress where you must put in name and email address although email doesn’t have to be confirmed.

Long time ago I was also planning to have that kind of script for WordPress, but it seems so expensive I think. But for now, a simple search on Google might help you out.