Shared hosting at webfaction. For the app (medical documents workflow) and scale (for small company, < 50 employees) webfaction is great. I could probably find a cheaper host but being able to work with support staff who actually understand coding and syadmin work is worth the slight extra cost.
Currently I use webfaction.com for two (nearly dead) projects but I'm considering linode.com or djangy.com for my next one. I've found webfaction to have <i>great</i> support but their RAM/cost ratio isn't so good.
Linode, their admin is great and been a customer for a long time, just a set up your self kind of deal but stackscripts are great for getting a server running quickly.
Amazon EC2 is always a good option. <a href="https://www.djangy.com/" rel="nofollow">https://www.djangy.com/</a> looks promising as a Heroku for Django.