There are many ways to use these domains, it really just depends on your goals. 1) You could create new landing pages for each domain to test conversion rates within your PPC campaigns.
2) You could build micro-sites on these domains targeting keyword variations or sub-keywords.
3) You could implement a server side redirect from them to your main URL so type in traffic will hit the main site.
4) You could park the domains and collect on any CPC revenue.
Since the extra domains contain your brand name you will obviously want to shy away from any risky testing to eliminate any risk to your brand.
