It would depend on your needs. For eg: do you need a L/W/M-AMP server or something that can run Rails, or node.js. If all you are doing is wordpress themes and templates, I assume you want a L/W/M-AMP server stack. AWS free tier is awesome and more suited to your needs. Once you start gaining momentum you will get charged, but hopefully you will be making positive revenue as well. Windows azure, they have a free 3 month trial, but it gets expensive there after. I personally use hostmonster, mainly because all the general server admin stuff that I do not want to worry about is taken care of for me. Their customer service is excellent as well. Other notable ones are Heroku, MediaTemple and Hostgator.