Wanted to add this "in" somewhere but I kept running into "This thread hasn't been ... for 2, 3 months ... consider starting ,,, ". So ...
There are a lot of opinions about plugins (WP) and seo, speed and so on. I haven't ever kept any of the seo plugins I've experimented with - But - If you want a very good tool get "broken link checker".
No magic shows, no miracle cures for websites and blogs, just a good solid tool. It works, it finds broken links, it emails you when it finds broken links, it lists them on a page, gives the linked text and a link to the post. I don't use the edit function, I go to the post, fix it, go back and choose "not broken".
I trust you'll find this as useful as I have - http://wordpress.org/extend/plugins/...-link-checker/