How can I repay some of the software companies that offer freeware programs (without donating money)?

Almost every computer utility I use, online or offline, is freeware that I’ve found through Lifehacker, or through some other reputable source. Many times these programs are really great for cleaning up my computer (Spybot, Revo Uninstaller, CCleaner, etc.), or my life (Toodledo, Mint.com, DropBox, or even Fluther). I very rarely drop a dime for any of these software companies, but I do want to support them and keep them in their freeware endeavors. What’s the best way to do that without shelling out cash (which would essentially negate the entire idea of open source or freeware)?

Oh yeah, and I’m not a programmer, so I don’t feel like I could contribute directly to open source software very handily.