Thanks so much Diego, that was helpful again.
In addition, I also found a good list of Intel Core-i-CPUs and their respective graphics units on Wikipedia.
It suggests that all CPUs based on the Westmere architecture still use Intel GMA or GMA HD and thus don't support OpenGL 3 (if I got that right).
Everything released on the Sandy or Ivy bridge seems to have at least the "HD Graphics" or even "HD Graphics 2000" and higher. This to me would mean they all do support OpenGL3 if latest drivers are installed, right?
Here's the chart, the page is in German, but the table is mostly numbers anyways :-)
Liste der Intel-Core-i-Prozessoren – Wikipedia
Have a nice weekend!
Bert