what kind of views should I use? I am going to download the Views module for a Drupal 7 website I am creating, but there are 2 different versions: There is the alpha3, the development snapshot, and another one that doesn't have a name I can see (it is highlighted in green). Which these three versions should I use?
It is really a personal decision on which one you should download. It is recommended to always download the one's in "Green". However views3 offers a significant improvement in the user interface and if you are just starting out in views, this might be a better choice.

A good article on choosing modules http://drupalwatchdog.com/1/1/module-selection-in-the-wild