Mountain View (we just moved onto the same street as YC)
BloomReach (<a href="http://www.bloomreach.com" >http://www.bloomreach.com</a>) is a small, fast-growing startup that is tackling one of the Internet’s most fundamental problems: helping leading online businesses get their highest quality, most relevant content found by their consumers, when and where they want it.  We're delivering a 95% uplift in non-branded organic search traffic for brands like Neiman-Marcus, William Sonoma, Buy.com and others.
Here's a Quora post why one of our engineers chose to work at BloomReach: <a href="http://www.quora.com/Stormy-Shippy/Posts/There-is-this-little-company-in-Mountain-View-that-I-work-for-called-BloomReach" >http://www.quora.com/Stormy-Shippy/Posts/There-is-this-littl...</a>
Backed by Bain and Lightspeed.  See our advisors here: 
<a href="http://www.bloomreach.com/who-we-are/our-investors-advisors/" >http://www.bloomreach.com/who-we-are/our-investors-advisors/</a>
Take a look at open engineering positions here: <a href="http://jobvite.com/m?37H9sfw9" >http://jobvite.com/m?37H9sfw9</a>
Email jason at bloomreach dot com if you'd like to chat before applying.  Interns welcome too.
We commit to moving through the interview process quickly with you, if you're interested.
Ask HN: Who Is Hiring? (September 2012)