SB 1.9.1 is the most current version.
SB 1.10.0 Beta 1 will be available soon.
I always send out email blasts for new versions. If you are not getting these, then it could be that you need to update your email address for your account and or make sure emails are not getting sent to spam.
I also always announce each release, so you can WATCH the announcements forum as well as the Sportsbook Demo thread (in which I also post updates on version releases).
One of the first places to always check is your customer account.
Click on the "Download Sportsbook" link for the specific Sportsbook License to access the downloads area. Versions are ordered Newest to Oldest (so that the latest version is always at the top).
NOTE: This works just like XenForo in that you are only able to download versions that are/were covered in your current or previous support/downloads agreement. If your support has expired, you;d need to get a 1 year extension in order to download newer versions that were not covered in your previous agreement (exactly like XF does).
As mentioned above, you might want to watch the Sportsbook Demo Info thread as I do post release updates in it.
The first post of the Demo thread always lists the most current version.
You can also watch the Announcements Forum as I post threads for each release.
Another thing I do that is helpful is TAG everything by release version. This way you can see a list of all Implemented Suggestions and Bug Fixes associated with a specific release.
Example of a release tag.
Sportsbook is also listed in the XenForo Resource Manager and is updated there as well (altho, I usually only post updates for 2nd point releases there).
I hope that helps