Unified Comm

Exchange server, then client machines, then mobile devices, then use the Outlook TZ Update tool. (See note below!)

By the way, Exchange-based Outlook TZ Update tool v2 is now available for download.

Update: It looks like I might have been incorrect on this one, as pointed out by Tim McCarty. Check out the official MS recommendations here.

You can download a handy ActiveSync installable DST update for your mobile phone/PocketPC here.

If you prefer to do it manually with a few premade CAB files, you can find them here for Smartphones and here for PocketPCs.

I think the easiest method, as long as you have ActiveSync or Windows Mobile Device Center installed, is to just use the ActiveSync .MSI installer on your desktop PC.

Something to be aware of as a possibility although it looks to be a fairly rare issue so far, thankfully!
You can read about it here.

It is still a very good idea to put KB 926666 on your Exchange server so that when March 15th comes along, everyone's calendar entries won't be off by an hour, unless you are blessed with not following daylight savings.

You can read about the mounting issue and the workaround here. I wish the workaround was not as complex as it is currently.