For $350, a wide angle with no severe barrel distortion will be hard to find. But, I'll give this a shot, in descending price order.
From Canon, the 10-22mm is pricy, but really versatile for a crop body. It does suffer from distortion and a lack of sharpness, but it is very wide, and if you upgrade to full frame, you can still use it if you pop out the body plug in it - albeit you have to be careful with your zoom range. You can occasionally find a 10-22mm for about $500 used, if they're beat up.
You also have the Tokina 11-16mm which is $450 from B&H brand new, so I suspect if you're lucky, you can find a used one for about $320-400. This is my main recommendation because of the price and great results from everyone I know who has one.
Finally, the Canon 17-85mm IS lens is goes fairly wide and is a great walk around lens. You can find these for less than $300 used.
Those are my recommendations. I haven't had personal experience with any others. I personally recommend the Tokina.