It really depends on your mortgage contract and how many years and houw much money outstanding.
If you just started your mortgage with 5 years term, you may want to max out your prepayment. And then keep the rest of you $$$$ into the TAX FREE account to earn interest. Note, you can keep $10,000 ($5k 2009 + $5K 2010) per person in the TFSA.
If you're toward the end of the contract, go sit down with your bank and find out the penalty of discharging your mortgage.