I purchased linux servers from them for my customers.  
I am purchasing a laptop for me today.  
My comment may be a little biased since I know the owner Gary, who's extremely knowledgeable about Linux. Plus they are not just a Linux business, they share the whole GNU/FOSS philosophy and constantly answer questions at the local Linux forums.  
LAC is a great and reliable Linux place.

As a long-time linux laptop user who was tired of  
struggling with unsupported name brand laptop  
hardware, I sought a serious tech oriented source  
of a totally linux-compatible machine. Having  
searched the web I saw Los Alamos Computers.  
 
Watching the site for a few months, I saw them  
keep their hardware at the cutting edge. When a  
nice clearance price on the previously offered  
laptop model appeared, I ordered. Delivery was  
exactly as promised. When some support materials  
I had expected were missing, a quick call got them  
sent promptly and free of charge.  
 
This group is a rarity: exactly what they appear  
to be. Like their web site, straightforward and  
tech friendly with all the data you need or want  
set out clearly. While they are Linux specialists  
with a great selection of system distributions,  
they will also install Windows for you if asked.  
Selling everything from dual-head power  
workstations to laptops, they clearly cater to a  
technically demanding market.  
 
For over a month, the laptop has performed  
beautifully. It is a fine custom design obviously  
made by and for linux fans. The system  
installation is similarly expert and logical. It  
would be virtually impossible to duplicate in the  
branded commercial laptop market.

I asked ResellerRatings to add LAC to its vendor list because I was pleasantly astounded by the quality of my experience.  
LAC sells computers running Linux, Windows and dual-boot, but Linux is their specialty.  
Buying a pre-built computer that runs Linux can be trying. Linux users want to control their systems in detail, but hardly any user knows enough about hardware, available drivers, etc., to make a completely informed choice about configuration. Here, LAC shines. I spent two weeks sending them e-mails, asking about this option or that. They patiently and promptly answered every e-mail until my education was complete and the computer specified.  
Even before the box shipped, they sent me the owner's manual in PDF and text, customized for the computer I'd ordered.  
When the box arrived, it came with CDs and instructions for restoring the computer to its as-shipped state. At one point, I did hose the system and had to use the disaster recovery set -- it worked like a charm.  
The box works great, but I have exercised LAC's technical support twice.  
Once, I issued two resets to the NIC and screwed up the firmware. LAC shipped me a loaner to confirm the problem, then replaced the card -- no questions asked.  
A week ago, the graphics card went south. When I reported the problem, LAC promptly shipped me a new one. Again, no questions, no waiting for the old card.  
They have paid shipping both ways, on both occasions.  
I had no idea until now that buying a new computer (especially a Linux computer) could be so pleasant. I would recommend this outfit to anyone.