A screen shot of the Direct2Drive website where you can buy and download games such as Dragon Age: Origins.

A couple of weeks ago I experienced the ultimate in gamer laziness: partway through playing Mass Effect 2 on the Xbox 360, I grumbled loudly because I had to get up off the couch to switch game discs.

It’s more than just a matter of surrendering that perfectly cultivated butt groove that you’ll never properly recapture, it’s that the whole concept of games existing on shiny silver pieces of plastic is starting to feel a bit outdated. In the age of fast Internet connections and massive hard drives, why should I have to leave the house to buy a game in the first place?

I don’t, of course. Games on demand – that is, buying games online and downloading them directly to your computer hard drive or game console – is exploding. Valve Software’s online Steam service for the PC saw a 25% rise in the users and a 205% increase in sales last year compared to the year prior, and even smaller sites such as the retro-gaming repository Good Old Games (www.GOG.com) have seen tremendous growth of late.

“When we started about 15 months ago, we had two publishers and around 30 games,” said Good Old Games spokesman Tom Ohle. “Now we have more than 180 games from 36 publishers and developers, including major names like Ubisoft and Activision.”

Not everyone has a fast enough Internet connection or enough monthly bandwidth capacity to make regular game downloading practical, and not all new games are available via download, although the number is growing every month.

Another significant drawback is that downloaded games can’t be loaned to friends or traded in once you’re done playing them – something that game publishers love, but is a disadvantage for gamers. On the plus side, you don’t have to worry about losing or damaging game discs, and most services allow you to re-download the game if it gets deleted or if you change machine.

Here’s a round-up of my favourite on-demand game sites. Discs? We don’t need no stinkin’ discs.

Steam (www.steampowered.com)

Launched five years ago by Half-Life creators Valve as a way of digitally distributing their own games, Steam now offers a staggering 1,000 PC games for download and has grown into a huge online community for gamers, with features like friends lists, achievements and in-game chat.

Steam is simple to use, downloads are reasonably fast and game updates are streamlined and easy to access. Because it can take several hours to download a multi-gigabyte game, Steam also allows users to “pre-load” some games in advance so that the game is fully downloaded and only needs to be activated on its official release date.

Direct2Drive (www.direct2drive.com)

Similar to Steam, Direct2Drive allows users to download entire PC games directly to their hard drive – hence the name – and offers a slightly more user-friendly online storefront. The community and after-purchase experience isn’t as slick as what you’d find on Steam, but Direct2Drive sometimes offers games that aren’t available on other sites.

Like its competitors, Direct2Drive walks new users through the process of setting up an account, making purchases (via credit card or PayPal) and downloading and installing the games. Unlike Steam, Direct2Drive also offers a selection of Mac games, including Dragon Age: Origins and The Sims 3.

Xbox Live, PlayStation Network, Wii Shop Channel

All three current game consoles offer a bevy of downloadable titles through their respective online services (assuming you’ve linked your console to your Internet connection), although these games are generally smaller, retro or independent titles that sell for $5 to $20.

In addition to the smaller games, Sony’s PlayStation Network sells new PSP games and some original PlayStation classics, while Xbox Live also offers a smattering of original Xbox games and newer (but not particularly recent) Xbox 360 titles, assuming you’ve got sufficient hard drive space on your console to store them. If you haven’t taken your game console online yet, you’re missing out.

Good Old Games (www.GOG.com)

This remains one of my favourite on-demand game sites. Not only do they they have classic games from yesteryear (modified to run without a hitch on modern PC hardware), but the games are dirt cheap – $5.99 or $9.99, depending on the title – and don’t have copy protection, so you can install them on every computer you own with no problems. Gems like the original Fallout and Fallout 2, Duke Nukem 3D, Heroes of Might and Magic, Arcanum, Myst and dozens more are all up for grabs, and each game includes a faithful digital recreation of the original instruction manual.