The Nature Conservancy has a carbon offset program that I use. They're credible. The money goes towards purchasing and managing land for forests and net carbon

The Nature Conservancy has a carbon offset program that I use. They're credible. The money goes towards purchasing and managing land for forests and net carbon removal. It's surprisingly cheap. They seem to have changed their site, though, and I can no longer find the page that allowed a direct carbon offset donation. Also, here in Oregon, you can pay the electric company a small fee (for me, about $11-12 a month) to guarantee that your electricity use is 100% offset by carbon-neutral generation (wind, solar, hydro, nuclear). Also in Oregon, you can pay the natural gas company a fee (for me, $5.50 per month) to offset your natural gas usage with "bio digesters." I'm more skeptical about their efficacy.