If you are working as a consultant, then the biggest advantage of incorporating will be in tax savings.
In Canada (Ontario specifically) there is a break-even point around $42k/yr income, where the personal income tax and corporate income tax (and accountant fees, etc.) you pay will be approximately equal. Above $42k/yr income, the corporate tax will become less and less compared to personal tax. This is due to the fact that the corporate tax rate is fixed at 16.5% (until $500k or $1M annual income... I can't recall) while personal tax rates have brackets that increase as you make more money.
To take an example from my past, the last year before I incorporated I made roughly $86,000 and paid about $22,000 in personal income taxes. The accountant that helped me incorporate did some calculating, and if I were incorporated, the corp would have had to pay only about $13,000-14,000 in taxes.
There are some costs associated with running a corporation. There are the initial costs of setting it up, usually between $2000-4000 for lawyers and accountants. Then annually, you will probably have an accountant prepare your corporate taxes, which will cost around $750-2000 depending on who does it and how organized your paperwork is. These are extra hassles that some people find unpalatable, and it is a bit of extra administrative work on your part, but altogether, it saves you thousands and is very much worth it. (Unless you have some kind of ADHD and psychologically cannot deal with paperwork.)
Another tax saving tool available in Canada is that you can make $50k/yr in dividend income, tax free. Therefore, if you and your significant other are both part owners in your newly formed corp, then you can essentially have a combined household (personal) income of $100k/yr, tax free because your corp will pay out dividends to its owners, rather than salary (which is all taxable). You will probably not make exactly $100k/yr tax free (but it will still be around $95k or $98k) because in order to take advantage of various tax credits you have to show some personal income. How this is works is that, whenever you need money from your corp, you just withdraw it. At the end of your fiscal year, you and your accountant will figure out how to label those withdrawals, be it dividends, salary, whatever, to maximize the tax savings. That is how I have been doing it in Canada, anyway, and your accountant will be more familiar with how this stuff works in your area.
The best thing you can do (aside from asking the experts on Slashdot, of course) is to go see an accountant who deals with corporate stuff. Explain to him or her what you are thinking about doing and outline your current situation. Using your 2011 net income as an example, they can then draw up a spreadsheet for you, showing what would be your taxes and other numbers if you had been incorporated in 2011. This will let you know with little uncertainty what is your best course of action.
There are other benefits that come with having a corporation, your corp can purchase the equipment (e.g. laptops, mobile devices for testing, etc.) that you will use to do the service that the corporation sells. This can be recorded as an expense of the corp, which reduces the corporate taxes. In contrast if you bought equipment personally, it would not affect your tax situation at all. This is nice if you like toys, and would like some extra reasons to rationalize their purchase.
In summary, if you plan to make more than $42k (*) this year from your moon-lighting activities, just get it done already.
* $42k, or whatever is the break-even number for the tax system you live in.