Shark is now hard to get. Fortunately, it's still available as part of CHUD in the developer downloads.
You may be able to get shark from here:
Click on developer tools, which should bring you to here:
Where you will find CHUD 4.6.2, which includes Shark 4.6.2 (227.9).
Unfortunately, this version does not seem to work with 64-bit kernels.
With new Macs it should come on the OS X DVD. This version, 4.7.3 (383), worked at first, but now no longer works:
11-05-31 3:52:50 PM [0x0-0x18e18e].com.apple.chud.modularshark WARNING: Length of the text section of com.apple.driver.AGPM 100.12.31 was reported to be 0xc000 (c pages) from the kernel, but we're using <VMUSymbolicator: 0x19f49350> (<VMUArchitecture: 0x19f47ca0> 0x1000007,0x3 64b - LittleEndian) /System/Library/Extensions/AppleGraphicsPowerManagement.kext/Contents/MacOS/AppleGraphicsPowerManagement that thinks the length is 0x9000 (9 pages). [-[KmodSymbolLookup _stretchedVersionOfSignature:withLocationReset:] (KmodSymbolLookup.m:708)]
It seems likely that Shark was broken by a kernel upgrade. I've filed an Apple bug report #9648225.
This problem was fixed for me by reinstalling XCode from the 10.6.6 DVD.