Game type: web based, html and flash.
Time demand: Whatever you want to put into it, although the more you put in, the more you get out.
Cost: Free, but with a lot of merchandise links, etc.
What it is:
This site has been online for years, and while it's gone more and more commercial over time, it's also still free at the bottom line.
On the surface, this is a "pet" game, where you adopt one of a decent number of different neopet breeds, then basically raise it up bit by bit. You can use the online currency to buy food for your pet, train its stats, fight with it in the arena, and buy a lot of other things such as your own neohouse and furniture/plants to decorate it with, collectable cards, collectable stamps, so on and so on.
But beyond that all of that, the site also works as a giant repository of original games, which you play in order to collect the currency which you then use for... whatever.
Now, when I say "original games," many of them are familiar, such as a general codebreaking game, a typing test, etc. But they all have some sort of neopets slant, and others are completely original. And there really is a huge variety of games, making it tough not to find at least a couple that you enjoy wasting time with. Random chance, games requiring strategy, puzzles... there's a whole lot here to offer.
The main downside for many would probably be the younger slant of a lot of the things, making it feel more like a "kiddy" site. But if you can put up with that, or just ignore it, there's a lot of entertainment to be had, and some of it might just float your boat.