20,000 Aeroplan Miles for AeroplanPlus Gold Card
The $120 annual fee Gold Card normally has a 15,000 point sign up, but until March 31, 2011, it's 20,000. (Thanks to TPG reader Martin for the tip).
To get your 20,000 points, apply here. You get 15,000 points after first use of the card and an addition 5,000 when you spent $1,000 in three months. Remember, this is a charge card, so if you don't pay off your balance monthly, you get hit with hideous interest rates, which will negate the value of any miles accrued.
You earn 1 mile for every dollar spent up to 10,000 and 1.25 thereafter and you can also add 2 cards for free, so get the whole family spending away (or open up cards for them since 20,000 miles for $125 is a steal- at least for the first year).