This is a nice new feature in Outlook 2010. Write your email message as usual and when you want to insert a screenshot, click the Insert tab, then click Screenshot.
You’ll then see a set of thumbnails of all your opened, unminimized windows.
Double click the one you want to insert and it will be added to your email.
That’s nice and easy, but if you’d like something more sophisticated, we’d recommend the free GadWin Printscreen screenshotting application, because with that you can choose exactly which area of the screen to capture. If you want even more sophistication and you don’t mind shelling out some money, SnagIt is another nice tool.