Open source software still has the unfortunate reputation of being inferior to commercial software. That might have been true once upon a time, but it's not anymore. Want an office suite that's up there with Microsoft Office? OpenOffice is a good one. How about some photo editing and graphics design software? The GIMP is fantastic. Laying out magazines and journals? Give Scribus a try.
While there's some junk software out there and there are some commercial products that are still superior to open source alternatives, you might be surprised at how much great stuff you can find for free.