11.5.502.110 is the latest version depending on the browser. Do remember you don't need to have more plug-ins installed than you actually use. For example, Chrome includes its own version of Flash.
And speaking of Chrome, Google also released a security update on the 6th (details). That's a rather easy update, just check About (chrome://chrome/) to see that you're running version 23.0.1271.64.
Apple released updates for the Windows version of QuickTime on November 7th (details). QuickTime 7.7.3 includes 9 updates for vulnerabilities which appear to be exploitable in drive-by attacks. QuickTime is no longer required by iTunes. If you don't remember the last time it was used, ask yourself, do you really need to have QuickTime installed? (It's a very popular target.)
Speaking of popular targets…
Java! Be sure your Java Runtime client is up to date. (Check your version here.) Our single biggest detection based on upstream data is: Exploit:Java/Majava.A. Java Runtime is the number one target bar none.
And the second most common detection based on our upstream data is: Exploit:W32/CVE-2010-0188.B. An exploit for Adobe Reader, which you can see from the CVE number, dates back to 2010. So make sure you're running the latest version of Adobe Reader.