By e-mail, I was asked a few questions, so I thought I'd share the answers here for everyone's benefit.
Q1: Did people downloading the initial spreadsheet (the one that got 100,000 downloads) need to enter their e-mail information in order to download it?
No, they didn't. I know modern defaults would have you grow an e-mail list, and would say that an e-mail address is a small price to pay for something of value. And they're probably right. But for a long time, I wasn't thinking there'd be more than the spreadsheet. I just made the spreadsheet to scratch an itch, and didn't see it as valuable enough to turn into a business. Eventually, I got frustrated with the spreadsheet for not being flexible enough, and knew that if I wanted it to live up to its potential, I'd need to turn it into a web app. Even then, for better or worse, I was thinking more about the product than "the business." I added an e-mail signup, but that was totally opt-in. At the time (2005, 2006), an e-mail address wasn't shared lightly (really; openly sharing e-mail was an invitation for spam; Gmail and its spam filters were neither as popular or effective as they are now).
A note about the e-mail list. When we launched the web app, I had high hopes that a significant number of the e-mail list would sign up (and pay). After all, these were interested people, right? They'd given me their e-mail address! I think we had 4,000 – 6,000 people on our list. So, of course, we'd end up with, like, 400 subscribers off of that, right? NOPE. In the end, I think it was .5% (so 5 out of every 1,000) that ended up subscribing. So, instead of 400 paying users, we had 20. It was a slow climb.
You can still download the spreadsheet if you like, at https://pearbudget.com/spreadsheet. It's free. And still has no e-mail gateway. I should probably change that at this point.
Q2: The spreadsheet: Did you release it on HN? Or were there other marketing channels?
No, didn't release it on HN. I think HN wasn't a gleam in Paul's eye at that point. Also, personal finance isn't something HN readers are as concerned about as they probably should be. So HN wouldn't have been the right vector, even if it had been around.
It was completely word-of-mouth. The one place that I can remember mentioning it was on MetaFilter's "Projects" page (in November of 2005), where the entirety of my post was: "PearBudget: Easy budgeting and finance-tracking for you GTD-types. Your money disappears. With a pocket full of receipts, 20 minutes a month, and this straightforward Excel spreadsheet, you can figure out where your money's going. It's free, so chalk that up as one place your money's not going."
At the time, the spreadsheet was far better than anything on the market, especially at the price point of $0. So I think people talked about it a fair amount. It eventually made it into Popular Science and a few other places. (The web app also got mentioned in several places, but I lose track of who talked about the spreadsheet and who talked about the web app.)
I think the leitmotif in all of this is that I wasn't trying to start a business. That just kind of happened. I've since tried to start another business, and that one didn't make it. I think the key thing was that I was passionate about this product, and kept wanting to make it better, and I wanted it to help other people, even (or especially) if they couldn't afford to pay for it. That is, my focus was on making the product and the world better, not on building a business. With the business that died, one of the main things that got in its way was my desire for it to be a business from the get-go. Maybe it would have died anyway. Hard to say. But I was concerned about things in Monotask like analytics and conversion rates and churn and marketing in ways that I wasn't concerned about for PearBudget, and those definitely distracted me from improving the product.
As to the original question, about marketing channels. I know the current / Lean Startup approach is to "charge from Day 1." I would encourage you to build something simple, cool, and useful, get it out there quickly, and see if people respond to it, before you worry about making it a business. If you're thinking of an e-book, get a sample chapter out there as a blog post, and see what kinds of attention it gets. If a web app, think about: what's the simplest way to do this? Hold lightly to it, but put heart into it. If it gets some traction, build on that. If not, think about why, and see if you need to take a different take on it.
One more thing, and I should have mentioned this in my earlier post. I started a podcast for webnerd/startup parents. http://donttouchthescreen.com. I only got two episodes in before putting it on hiatus, but I'm thinking about starting it up again. If folks here would be interested in that, let me know by Twitter (@charliepark). Thanks.