I'm having pretty good, "ok" success with a dog training sites opt-in newsletter sign-ups. Since I've been running it, I've gotten close to 100 people who are wanting my new newsletter. This means I have 100 people who I send original dog training articles and such via my newsletter. This means that I'm building trust with them. And every marketer knows what that means! Since dog training (specifically obedience and protection) is one of my loves, I really enjoy writing the articles, and once I find a really good drop shipper (anyone recommended?) for dog training equipment, I'll begin the marketing towards this highly interested and targeted/ relevant audience.