[petercooper]

Email lists are very, very important. I was also able to market my freelancing book to 2,000+ freelancers on my Planscope list.

I'll second this (along with the scores of people I've discussed this topic with) because I accidentally turned this into my full-time business!

I started my Ruby Weekly newsletter merely with the goal of promoting books and screencasts I wanted to make but it has gone a bit too well and now I have 75k subscribers to speak with. Sadly still no books.. but the training and screencasts have gone well.

[bdunn]

And because you're dishing out a weekly email, you're keeping the list healthy and motivated.

I've made the mistake (and I know a lot of other's have too) of: build email list, silence, silence, silence, SELL SELL SELL. ...And then Mailchimp contacts you about your unsubscribe rate being too high :-)

[nathanbarry]

Wow! That is an incredible number of subscribers. Sounds like it is time to write that book. I am now at $11.5k in less than 24 hours. With a list like that you could do a lot better.