Quark was the leader (maybe still is a bit), but Adobe's InDesign has come on very strong. My main client switched to InDesign last year and has been very happy.
That said, there really aren't any cheap page layout programs. There also aren't many to choose from. It's essentially Quark or InDesign. Pagemaker is also owned by Adobe, but that was discontinued at least a year ago. I think you can still find copies around, but there's no sense throwing money at a dead end product. Other than that, there's Apple's own Pages (part of the iWork package). Being a fairly new product, it lacks quite a bit compared to Quark or InDesign. I imagine documents produced from it get scowling looks from professional print shops. They don't like having to deal with non standard documents. And unless it was added to version 2, Pages also doesn't support CMYK.
Edit: Yeah, yeah. That too! What eww said. Don't even consider for a second trying to use Word as a page layout program. It's as good at that as it is for building web pages. In other words, it stinks. Press and prepress shops will hate you forever if you send them a Word document as your brochure layout. They will happily take it though after informing you that they'll have to rebuild the entire project for you in Quark or InDesign. At your cost, of course.
Edit number two: Found two other lesser know page layout apps.
Create, which runs $149. And
Swift Publisher for $35. But again, you'd be using programs that press shops would be unlikely to accept. If nothing else though, Swift Publisher is cheap enough that you could at least get used to how a page layout app works before investing in the much more expensive Quark or InDesign.