When looking for a great view of the Strip you might think about something like Ghostbar at The Palms, The High Roller, or perhaps Voodoo Lounge at Rio.
Those places are great, but if you're looking for a nice view and don't want to spend any money - several of the hotel parking garages around the Strip can give you a nice view for absolutely free.
Here are some pictures I got recently from the Rio parking garage. The view isn't quite as nice as Voodoo lounge, but it's not bad.