I believe all these are wide angle only, not fish eyes, should keep the lines straight etc. 3rd part lenses generally have mounts to suit any brand and brand specific lenses will only work with that brand.

Nikon AF-S 12-24mm f/4 $1800 (!) (only for nikon)
Canon EFS 10-22mm f3.5 - 4.5 USM $1200 (only for canon)
Pentax 12-24 F4 SMC DA ED AL IF $1100 (only for pentax)
SONY DT11-18MM F4.5-5.6 $1200 (for sony mount)
OLYMPUS ZUIKO DIGITAL 11-22mm F2.8-3.5 $1220 (for olympus)
Olympus 12-60 F2.8-4.0 SWD Lens $1500 (for olympus, best range of zoom here)
Olympus ZUIKO DIGITAL 7-14mm f4 $2300 (i think this might be a fish)

Sigma 10-20mm F4-5.6 EX DC $800 (available for any camera)
Sigma 12-24mm F4.5-5.6 EX DG ASPHERICAL HSM $1000 (any mount)
Tokina AT-X 116 PRO DX 11-16mm F2.8 $1200 (canon or nikon only)
Tokina AT-X 124 PRO DX 12-24mm F4 $1100 (lots of mounts)
Tamron SP AF 10-24mm F3.5-4.5 Di ll LD $900 (canon $800 and lots of other mounts)
Tamron AF11-18mm F/4.5-5.6 Di-II LD Aspherical $1000 (sony, canon, nikon)

So that tokina is the fastest here, but also the smallest range. Not sure if its any good but im going to look into it.

Just a note on those canon mounts if its EF-S means it will only fit a Crop sensor Camera.

Also forgot this one

Sigma 12-24mm F4.5-5.6 EX DG ASPHERICAL HSM Canon/Nikon $1200 ish

okay added it, doesnt seem like a good choice compared to the other sigma however, id assume most people would want the shorter end rather than the longer.

Yeah your right. Gee like to see 10 mm on fullframe

well apparently it works but you end up with a solid black circle border 10-12mm from 13mm up it fills the frame okay, so i guess the 12 is the better option for full framers.

yeah of course.. cool.. Yeah i love my 12mm..

How about these also:

Pentax Lens 10-17mm f/3.5-4.5 F/E DA $819.00
Pentax Lens 16-45mm f/4 ED AL DA $442.00
Pentax Lens 16-50mm f/2.8 DA* ED AL [IF] SDM $1399.00

Sigma Lens 15-30mm f/3.5-4.5 EX DG ASP $919.00

Short review of the $442 lens and the whole wide view thing can be found here:
Here

I'm wondering if a Pentax K20D and the Pentax Lens 16-45mm f/4 ED AL DA (read reviwe first) for about $1600 might be compareable to some of the Canon/Nikon packages for D60/450D?

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My favorite lens on full frame

Don't you have a 5d?? I thought sigma 12-24 was an EF-S type mount and therefore not compatible with the full frame??

16-35L for the full frame or the 14 prime

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Yeah i do have a 5D and that lens isnt ef-s it fit full frame Nicely
About to buy a 5D Mark2 as well Cant wait.