Whenever there's a maintenance release for a device, it's posted individually as a new thread on the device's sub-community. You can currently go to the device's support page to see a consolidated list of all updates for the device, however, there is also a blog that now shows all updates to the device.
By subscribing to the blog you can receive notifications whenever there are software updates available. Comments have been restricted on the blog - I will continue to post a new thread when an update is available and comments should be noted in that thread (as usual).
Access the LG Optimus S Maintenance Release blog here. To subscribe to the blog, go to 'I want to' in the upper right hand corner of the blog and select 'subscribe'.