I know of Nessus (which is $1300 for a pro feed) and OpenVAS (which I don't like).
I use Linux so do I have any other options for vulnerability detection?
To expand on the other Rory's list a bit, if you're using Linux for VA style activities the main one I'm aware of in addition to Nessus and OpenVAS is
If you're using windows for VA there's also
Those two are general VA products. On top of that there's managed services (eg, Qualys) and tools that are more specific in nature (eg, web app. scanners like IBM Appscan and Arachni).
There are quite a few (read loads) in this space. Some examples:
The following offer internal or external vulnerability scanning and management
Then you have web vulnerability scanners like nikto and code assessment tools like Fortify
Have a read of Fyodor's sectools list
Sorry for the delay, I've found this page today.
I'm using a VA solution called IKare that includes OpenVas and Nmap. Even if you don't like Openvas, the UI is cool and the solution run well and fast for discovering and VA (scanners are ready-to-go). The solution is more oriented to monitoring to perform daily or weekly scans.