As discussed by the Office Sustained Engineering group cumulative updates for all Office Products including WSS 3.0 and SharePoint 2007 will be released every second month.
Yesterday we released the so called April Cumulative Update. The so called "Uber" packages for MOSS will be released in a couple of days. Currently you can download the individual global and localized fixes for your specific language packs.
Be aware that this is the first Post-SP2 hotfix! That means it is highly recommended to install Service Pack 2 before installing the April CU.
Details and download locations can be found in the blog my colleague Joerg Sinemus published: