As a SharePoint Administrator, you will see a plethora of updates released overtime to resolve numerous issues as well as add new functionality, however SharePoint does not make patching very easy or intuitive for a newcomer.
Patches for SharePoint Server 2007 are actually two-fold although you will find it hard to locate a source which tells you this definitively. SharePoint Server 2007 is a combination of Windows SharePoint Services 3.0 (WSS) and Microsoft Office SharePoint Server (MOSS). When you come to patch SharePoint installations, you need to install updates for both components, and you need to install the WSS updates first.
The second thing to note is that all SharePoint updates of late are cumulative – You can jump straight to the latest and greatest without needing to install previous updates, so long as you have a service pack installed. All of the recent Cumulative Update packages from Microsoft have a minimum requirement of Service Pack 2 for WSS and MOSS.
You can download Service Pack 2 for WSS and MOSS from the following links:
Windows SharePoint Services 3.0 (WSS) Service Pack 2
Microsoft Office Servers Service Pack 2
At the time of writing, the most recent Cumulative Update for SharePoint 2007 and WSS 3.0 is the June 2010 updates which you can download as follows:
Windows SharePoint Services 3.0 (WSS) June 2010 Cumulative Update
SharePoint Server 2007 June 2010 Cumulative Update
As a side note, for those planning an installation of SharePoint 2007 on Windows Server 2008 R2, you must slipstream the Service Pack 2 components of WSS and MOSS into the DVD media to be able to complete the installation otherwise you will receive reports of an unsupported operating system and will not be able to proceed with the installation.
This time next week, I will hopefully be blogging about my experiences performing a SharePoint 2010 upgrade, so keep yourself posted.