Widget to show calendar events and TODO items merged in a single agenda?
You might want to take a look at Pure Calendar Widget. Will cost you about two bucks, but does exactly what you request:


  Widget for Agenda / Tasks / TODO (agenda style)
  
  
  Synced with Google calendars
  Show calendars from Google, TouchDown &amp; Moto/LG Exchange
  Show tasks from Astrid, Tasks (Team), MyPhoneExplorer, Ultimate To-Do List, TaskSync, CalenGoo, DGT Gtd, gTasks, Got To Do, Task Organizer, Due Today, TouchDown, Pocket Informant
  


 
Pure Calendar Widget / Agenda Widget for Android (source: Google Play; click image for larger variant)

An alternative could be Agenda Widget for Android (second screenshot above), which has a free trial variant (which I linked) and comes close to what the previously mentioned does.

As I don't use any of those, I cannot tell you which might fit you best -- but at least with the free variant, you might want to give it a try :)