The Canon 200mm f2.8 L is superb. It costs less than $1000 to get from overseas and is well worth the money IMO.
The other gem is the Canon 50mm f1.8, the cheapest lens in their line up but very sharp
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Of the zooms I have heard good things about 70-200 f4.
Don't know too much about the wider angles, although I have heard the 24mm f2.8 is a good performer for astrophotography.
I have assumed you're not wanting to spend megabucks as there are better lens but you have to pay (i.e the Canon 200 f1.8L costs around $5000 SECONDHAND).
Terry