I used to be a bit nervous of MODS, I wasn't sure how to install them and I thought they might destabilise the game but then I watched http://www.youtube.com/watch?v=n_ix-dOGfXs&feature=related (you only need to watch half of part 1) which explained how to use the http://www.newvegasnexus.com/downloads/file.php?id=36901(FOMM) to install and manage them.
They can add whole new areas of content, like my current favourite "A World of Pain", add interiors to boarded up building, improve the look of the game or just make minor changes like adding location points to Camp McCarran or removing the Strips interior gates.
Just about every wish or complaint I read on this forum can be answered with just a tiny download, you don't have to wish for a ghoul companion or some F3 weapon was available, you can have it and yet not that many people seem to use them, so this thread is to encourage people who haven't done so yet to give them a go.