If you select Blogs, Monitors or Spaces from the navigation bar then you will be able to see a list of groups of those types. However, not all will be listed. Some groups are private and so will not show up in these indexes, even if you are a member.
To go to a private group that you are a member of, see How do I go to a group that I am a member of?
1.0.0
Why private groups are not show in the group index pages.