I am looking for resources for learning MS Build (not just books). At the moment, I am mainly engaged in combining assemblies and automating build tasks. (night assemblies, etc.)
Neither merging nor assembly automation has much to do with MSBuild. You will need ILMerge and, say, CruiseControl.NET.
Have you looked at online docs?
http://msdn.microsoft.com/en-us/library/dd393574.aspx
I use the previously mentioned documents, but they were not really useful for learning MSBuild. For this, I turned to "Inside Microsoft Build Engine: Using MSBuild and Team Foundation Build . " After reading it and exploring all the concepts of MSBuild, I now use the MSBuild document as a reference. They finally make sense.