Newegg has a nice selection of rackmount cases.
http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=100007731%20600029570&IsNodeId=1&name=Rackmount
Depending on your needs, I highly recommend a rackmount case.
Pros are: sturdiest type of case. The better ones you could smack with a bat and not damage the internals. Excellent heat-dissipation, airflow and spacious and roomy to build in. Looks awesome. Systems mounted in a rack enclosure look uber-professional. Surprisingly inexpensive for the level of quality you can get.
Cons: Heavy! Definitely not for a system you plan to move around a lot, unless it's in a cabinet on wheels.
A couple years ago I built a kickass rackmount video editing system for a small business.
Mounted inside a $40 rack cabinet. Client loved it- their total cost was $12K but the same setup would have cost them twice as much as a turnkey.
I used this case:
http://www.newegg.com/Product/Product.aspx?Item=N82E16811182566
Also did a more recent build with this case:
http://www.newegg.com/Product/Product.aspx?Item=N82E16811321005
Make sure you get the right type for your motherboard type. A couple of times I've had to make modifications to accomodate features of a desktop motherboard vs. server motherboard. (Example: back facing SATA ports as opposed to top facing. Some designs these will have your SATA connections running into the hard drive cage.)
You can see it's a pretty tight fit here, and I had to cut away part of the drive cage support structure to be able to reach all the rear-facing SATA ports:
