This very morning Apple released Snow Leopard update 10.6.3. It's available via Software Update, or (preferably) from Apple's download page. I'm downloading it now.
As always, wait a week for the reports to come in, and for my own experience with it. I will be installing it today after making a clone backup of my hard drive so I can revert to 10.6.2 if I need to.
If you go ahead and do it, be sure to open Disk Utility and Repair Permissions, both before and after the update. For a list of the patches, fixes and updates, visit today's Macintouch as well as MacFixIt and Apple's own site.
Also coming is iTunes 9.1 with support for the iPad and the Books section of the iTunes Store. I'm going to skip the iPad thing simply because I kept track of the web sites that use Flash that I visit regularly (excluding video sites) and found too many to make the Pad a useful device for me.
Your mileage may vary. A lot of people will love it immediately. If you are an early iPad adopter I would be interested in hearing your experiences with it.
Also released today is a Security Update for users of 10.5.8 (2010-002). It contains the same security patches as the ones in the Snow Leopard general update, but since Apple has made more mistakes with security updates than any others they have issued, I quarantine this for an absolute wait of at least two weeks before installing it.
There is no corresponding security update for Tiger 10.4.11, which appears to no longer be supported. Some of you still dependent on Classic OS9 applications must stay with Tiger and PowerPC Macs forever, so be aware of that as you look toward future upgrades. Leopard abandoned support for Classic and Snow Leopard abandoned support for AppleTalk printers.
Most people (including me) who want to keep access to these old programs and equipment have an old Mac dedicated to that service, which you will want to keep in good shape with utility repair programs such as Disk Warrior 2 and Norton Utilities 7. Fortunately, old Macs can be had for next to nothing, with G3 iMacs going for about $70 at FreeGeek and Craigslist, and older SCSI models like the beige G3, the 7600 and the SE-30 showing up in thrift shops. If you use one, start shopping around for a backup unit; even these well-made models die eventually.
PS: Anyone need an old van for moving lots of people and/or stuff? I'm selling my 1990 Ford van conversion, which I no longer need now that I traded in my SmartCar for a Nissan Cube. See it at Craigslist.