You can search for them here: http://openports.se/
The only problem with OpenBSD in regards to 3rd party apps is that updates are only build against -current. So, if you run a release, you don't get any package updates, not even for security vulnerabilities. Only apps in the base install (like ssh and nginx) get updates. FreeBSD's ports tree, by contrast, is not separated by development branches, so you can always get the latest ports tree as long as the release is supported. The same tree that works for -current also works for the supported legacy release.