Go to www.download.com. They have quite a selection of free software. Mozilla.org is another good site; all their stuff is free. If there's a specific type of application you want, Google might help you find out if there are free versions of it. On the subject of Google, Picasa is a decent free photo organizer, and a lot of people like their free Chrome browser; GMail is also free. Afaik, Microsoft's free "Windows Live" suite should work in Windows 8 also. Www.libreoffice.org is another good one. Adobe.com has free software.
Edit: I'm sure you didn't mean Windows 8 itself. For that, if you buy the product key from Microsoft, you can then download the software, free.