Gary McKinnon was arrested in 2002 for breaching security systems at Nasa and the Pentagon.
His actions were described as "the biggest military computer hack of all time".
The UK Government turned down extradition requests from the US, where he faced up to 60 years in jail.
Medical experts had warned that Mr McKinnon — an Asperger's sufferer— would be a suicide risk if extradited.
Now, for £40 an hour, small firms can receive advice on search engine optimisation (SEO) from him.
On his Small SEO website, Mr McKinnon writes: "My aim is to provide high-quality SEO to small businesses and individuals. All of my clients have so far reached the first page of Google search results for their primary keywords."
He added: "I charge £40 per hour, with most clients only needing five or six hours of work on my part, and taking around two or three months to get to page one.
"The increase in traffic to your website and sales from that traffic is a great return on a small investment. I don't use techniques that result in your website falling out of favour, and this ensures your long-term, high-quality ranking on Google, Bing and Yahoo."