No doubt you’ve already heard: Valve Software’s Steam software is now out for the Mac, and the company has also released its own award-winning game, Portal, for free until May 24th.

PC users have had Steam for ages, and now the Mac is that much more viable a platform for “serious gaming”. Steam is sort of an iTunes for games, a distribution and marketing channel through which users can browse offerings from many different developers, both indies and majors. It’s a software storefront, and it has been very, very successful. Expect many more companies to consider producing Mac versions of their games now that there’s a trusted, centralized way to put said products in front of buyers.