You can find a list of the app ecosystem here.
Note that there could be applications missing (developers don't need permission to deploy, so we don't know all the applications). Also, these are applications that we know about, not necessarily ones we endorse (we don't have the bandwidth to audit every application on Optimism). Please use at your own risk and be sure to always do your own research before using this technology.
If you are a developer and your application is missing, please submit it here.