I've installed a few off grid systems like you described, and the first thing I can tell you is that if utility power is available, it will be a lot cheaper than powering through solar/wind alone. If not, it can be done, and can be pretty slick.
You'd be looking at what we refer to as a "hybrid system". That means that you would have the solar/wind to run most, and a generator to make up for poor weather, or heavy loads. Four parts to the system.
Inverters- Main components that convert the DC into AC, and are the brains of the entire operation. These are sized by how much power you are going to need at any one time. If it's just you using one machine, and some lights, it doesn't take much. If it's a couple machines, a compressor, AC, lighting, and a bunch of neon lights, it may need to be a lot of inverting power. These are nice machines that I usually use for my projects.
http://www.outbackpower.com/index.php/outback-products/integrated-systems/item/flexpower-two?category_id=441
Batteries- Power source of the inverters. The size of the battery bank is determined by how much power you will use over a set period of time. That time frame is based on how long you may be without sun or wind. Most of the time we figure on 3 days of normal use without help from the sun before the bank is depleted (discharged to factory recommended state, not 100% empty)
Solar/ wind- primary source of power to charge battery bank. Sized according to time available to charge the battery bank, and the total capacity of bank. For a weekend home, smaller works because the solar has all week to charge. On a daily use home, it needs to be big enough to handle 100% of the power needed, plus extra to make up for low production days. If the system will be used year round, figure out sizing based on winter production.
Generator- Backup for lack of sun/wind, or to handle out of the ordinary power needs. With a good, pad mounted, auto start generator, the inverter can be programmed to start it up whenever the batteries need the extra charging capacity. If you don't mind the generator running more often, it can allow you to reduce the size of the battery bank, and Solar/wind system.