What about 14mm f/2.8 D? It's a little bit expensive for begginers, but it would go nicely with D90 and it has ~20mm on DX cameras. No autofocus on D60.
There are also some fisheyes (10mm f/2.8G DX, and 16mm f/2,8D) which are less expensive, but I dont think you are after that...
I'm just mentioning, it's not a recommendation or something.
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Nikon D60 + kit lens
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