I've had good luck with free to $10 cards - a b card about a year and half ago from PC Club ($50 w/ a $50 rebate), and have now upgraded to a Belkin g card for $10 after $40 worth of rebates at Staples.

b is fine for throughput if you are just surfing at NRT, but g has better range (or so I've been told) which is nice when the signal strength is poor (as it so often is).