Continue finding good stuff on the NirSoft site.
Not sure how many times I had to use "at" command on embedded. Especially when I had to launch a command line within LocalSystem context (/interactive switch). Although always had to calculate timing and do a few additional commands in order to schedule and then delete the properly configured "at" command. Now I won't have all this problems with another NirSoft's utility - AtNow
Some good stuff for doing Window sniffing - from class names to style/ex-styles and etc. Two really nice utilities - WinListener and WinExplorer. The second is really good as it allows you to modify all the windows parameters via GUI instead of messing with the code and SetWindowsPos API calls.
Tools like ExeInfo and DLL Export Viewer are also nice. But there are lots of similar tools on the Web. Also, I am a fan of FAR Commander and a few plug-ins there do similar PE analisys and produces even better, more detail and visual results.
In driver and service area - ServiWin. Not as good as devcon but nice GUI makes it easier to see and filter out specific driver services. Also, it shows dependencies which is realy helpful on XP Embedded.
The CurrProcess tool is an extremely simplified clone of ProcessExplorer from sysinternals. Advantages - small and requires less dependencies in the image.
ActiveXHelper could be considered as an embedded [read: simplified] version of Microsoft OLEView tool.
DumpEDID and MonitorInfoView -interesting tools. Don't yet know how I am going to use them but I will.
USBDeview - useful, no doubt. Especially the stop/disconnect function. Although if I needed more info on a particular USB device or even a deep look into the interfaces and protocols exposed by the device, I would use an USB Analyzer.
ShellExView - could be useful when dealing with Shell extensions and namespaces issues.
OpenedFilesView - I am probably going to switch to this from similar sysinternals tools.
Many, many more tools there. Explore the utils part of the website by yourself!