Kalzmeus on SEO (click around his blog for more, guy's a genius): http://www.kalzumeus.com/2010/01/24/startup-seo/
Also some quick, simple advice:
1. Blog 2/3 times per week minimum. Target a single, relevant keyword per blog post (relevant to your domain). The post title, H1s, H2s etc, image tags should all contain your primary keyword. Blog posts don't have to be long, but they do have to be useful.
2. Build a G+, FB, Twitter account for your site if you haven't already. Blast out your new posts to these accounts using Hootsuite (free, but you can pay if you like).
3. Build an audience on the social networks - just search around, follow relevant people and share useful, educational material. Don't spam.
4. Personalised mass email from Google Docs and Gmail (kind of hesitant to recommend this in light of Google shuttering services!): http://www.labnol.org/internet/personalized-mail-merge-in-gm... you need to have "newsletter" signs ups (blast out a digest of your blog posts once per month), calls to actions etc on your site for this to work properly (i.e. optimise your site to capture names & emails). Great, low cost/free way to make sure your audience stays engaged and coming back to your site. You can pay for this kind of service too, e.g. Mailchimp (they've a free tier), Constant Contact, or the likes of Hubspot for full suite of marketing automation tools.
5. Best of Startup marketing/SEO here, that I've compiled over the years (absolute gold): https://docs.google.com/spreadsheet/ccc?key=0Ag_fyIIMSJ6DdGt...
6. Check out Sell More Software by patio11: http://www.hyperink.com/Sell-More-Software-Website-Conversio...
Many engineers don't fully appreciate marketing as patio11 would be quick to point out, but there's a start.
I would seek out professional SEO company's and try to find the best deal. No way anybody could do all this stuff by themselves. In the end, it will be a worthwhile investment. From my own experience it's very time consuming to get it right.
However if you're a bootstrapped company, you may not have a choice but to put the time in yourself rather than paying for professional SEO services.
If you have a technical and non-technical co-founders, this list is a large chunk of what the non-technical guy should/will be doing.
Building a great product that people want is pointless without letting people know about it.
That kind of thing is never going to help
http://validator.w3.org/check?uri=http%3A%2F%2Fsearchco.de%2...