You aren't going to lack for things to do in Las Vegas. More than likely, you've come here for the gambling, which should keep you pretty busy. (We say that with some understatement.) But you can't sit at a slot machine forever. (Or maybe you can.) In any event, it shouldn't be too hard to find ways to fill your time between poker hands.
Just walking on the Strip and gazing at the gaudy, garish, absurd wonder of it all can occupy quite a lot of time. This is the number-one activity we recommend in Vegas; at night, it is a mind-boggling sight. And, of course, there are shows and plenty of other nighttime entertainment. Vegas is firmly set in such an "adult" entertainment direction that many attractions, particularly those with kid appeal, have closed, and though new, equally expensive options may come along to take their place, the emphasis right now seems to be on mature fun -- drinking, gambling, nightclubbing, and the like.
Don't forget to check out the free hotel attractions, such as Bellagio's water-fountain ballet, The Mirage's volcano, the MGM lions, and the Show in the Sky at the Rio. Oh, yeah, and the utter piece of hooey that masquerades as the pirate show at Treasure Island. You can probably give that a miss.
You could also consider using a spa at a major hotel; they seem too pricey (as high as $30 a day) to fill in for your daily gym visit if you are just going to use a few machines, but spending a couple of hours working out, sweating out Vegas toxins in the steam room, and generally pampering yourself will leave you feeling relaxed, refreshed, and ready to go all night again.
There are also plenty of out-of-town sightseeing options, such as Hoover Dam (a major tourist destination), Red Rock Canyon, and excursions to the Grand Canyon.
