It's possible to do all the grouping and ungrouping of slide objects in PowerPoint 2007 with menus and contextual Ribbon tabs, depending upon which version of PowerPoint you are using but it's even quicker to do it with shortcut keys.
Again, depending upon which version of PowerPoint you are using, the shortcut keys may differ. Here's a listing to help you:
PowerPoint 2002 and 2003:
Group: Ctrl + Shift + G
Ungroup: Ctrl + Shift + H
PowerPoint 2007 and Higher:
Group: Ctrl + G
Ungroup: Ctrl + Shift + G
It's sort of ironical that the Group shortcut key in PowerPoint 2003 is the same as the Ungroup shortcut key in PowerPoint 2007.