Did you execute any end-user license agreements (EULA)? That is, did you have to click to agree to join a site from which you get material? If so, that EULA most likely prohibits you from scraping, copying, etc. In that case, if you violate the EULA, the site could come after you for the remedies set forth in the agreement, regardless of copyright law. Keep in mind that EULAs that require assent (click to agree, check this box, etc.) are different from, and much more likely to be enforceable, than a terms-of-use statement found at a website.
How much material are you taking? What type of material are you taking? Job postings typically are comprised of two copyrights: a copyright in the listings -- the words and expression of the listing -- and a compilation copyright for the database collection, organization and selection of listings. As a job search engine, you are not likely to infringe the compilation because each search that you generate likely accesses a small percentage of each database collection. (Although there's no bright line test for compilations, courts have permitted copying of over 70% of some compilations.) As for copying the "expression" in the job listing, the more expressive or unique the writing in the job listing -- for example, funny or flowery listings -- the harder it is to justify copying the complete listing. That may explain why search engines typically only include the first sentence or two from search results. Of course, most job listings, like apartment rental listings, have a minimal level of originality and are primarily a collection of uncopyrightable facts. So you're not likely to run into problems.
Finally ... avoid creating any claims or implication of association or endorsement -- for example, stating "We search for jobs at Apple and Microsoft."