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 December Cumulative Update.
There is a chance to the way we will release cumulative updates from now on. In the past we shipped localized and global cummulative updates in separate packages. Not with each hotfix build there was a localized patch. So it was a little bit complicate to get your system to the latest patch level as you had to install at least 4 fixes (see Joergs instructions on installing the October CU to understand what I mean).
The December CU is the first fix which will be released in two formats:
1) The same way as before through the following fixes (notice that no localized MOSS fix has been released in December):
2) A real cummulative update which contains all previous fixes including latest global and latest localized for WSS and MOSS:
The fixes for the second format are much bigger as they always contain latest global and latest localized fix.
The benefit is that you will always be on the latest patch level and that there is no need any more to install the Infrastructure update in addition.
[Update December 18th] Also have a look at the following article from the SharePoint Product group.