It is my understanding that there are no penalties for withdrawals and you can withdraw as much as you want as often as you want, including more than once in the same calendar year. Of course, the money must be in cash in the TFSA, which may require you to sell something. That sale may have fees associated with it and possibly penalties for early withdrawal, etc.
There is still huge confusion over this, because there are penalties for over-contributions in the calendar year. You contribution limit is still $5,500/year, regardless of how much you may have withdrawn in that same calendar year.
So if you withdraw $10K in 2013, you can still only contribute $5,500 in 2013. In 2014, you can contribute $5,500, PLUS you can also contribute an additional $10K for the 2013 withdrawal of $10K. Think of it like 2 separate limits, one for current year, and one a running total of all past withdrawals.