Yep, I got two interviews on the basis of spec applications. Make sure you really target the letter and your CV to the organisation! Follow up your spec application with a phone call. I felt like an idiot doing this and, yep, some people are very busy and will give you the brush off but I found one guy who was high up who wanted to pick my brain and I got an interview out of it. Turned out I took another job, but, in the end, what's the harm in trying?