GIMP: http://gimp.org - Gimp is for doing photo editing work. People hate on the gimp for not have 16 bit color support, but this point should be moot for the overwhelming majority of users. I've used GIMP to edit photos, then sold them on iStockphoto where they have been used in advertising.
I've been using gimp for ~10 years and I've never come across something that I can't do with it. (Including the "content aware fill" thing from about a year ago: http://newslily.com/blogs/96). I'm a pretty big GIMP fan.
People also hate on it's interface. If you've grown up on photoshop, sure, but I can work faster in GIMP than I can in anything (including photoshop).
Inkscape: http://inkscape.org/ - I use inkscape every single day for doing advertising materials at my job. I've done ads that have been published in nationally-syndicated magazines with this, and have done work for enormous, internationally-recognized brands with this. Inkscape is a fantastic piece of software.
Scribus: http://scribus.org - Scribus is for doing page layouts. While I don't use it extensively anymore, I have used it for publishing work in the past. It is a fantastic, very complete piece of software that will do everything that you want to do with it.
This stuff is all free, and is all fully capable of allowing you to do work. The only things you're going to get with Adobe's products is support for their proprietary formats.