Sorry I don't use TimeMachine, but just realize that TimeMachine is a rotational backup, eventually older stuff gets deleted.
If you want to keep things pernamently you need to seek other backup solutions
So I have finally used time machine to back up my data. If I run a clean install of my OS and want to add say Pages or Google SketchUp back onto my laptop do I just drag and drop?
If you erase your entire system and install OSX, you'll be asked if you want to transfer your data (that's Setup Assistant). You can select or omit broad categories of things: apps, user home folders and/or the sub-folders in user home folders, such as Desktop, Documents, Picutres, etc. But you can't pick and choose individual apps or files. See Using Setup Assistant on Snow Leopard or Leopard for the gory details.
Drag and drop from TM backups may or may not work; if you set up a new user account, then drag selected items from the backups, you may have permissions problems with the files.