I actually built a semantic engine for CV/job ad matching last year but I could never get over the feeling that it's not really what people want - so it's sitting dormant in my pile of ideas-I-never-launched.
I do recruiting and because I'm a developer, matching is pretty trivial. But most recruiters don't have any serious dev experience, so if they need to search through a big database of resumes, this could help. Assuming you don't factor in that resumes are largely worthless :-)
1. http://blog.alinelerner.com/building-a-product-in-the-techni...