Here's another reference I use all the time.  Just go to Appendices->Technical References and Datasheets ->Z80 Instruction Set.

Oh. Those are machine cycles. Since the shortest instruction is 4 T-cycles (I like to use the term "clock cycle" or CC for this), it might be easier to represent some instructions in terms of machine cycles. The only real benefit is dealing with smaller numbers, though I don't really like using them because of all those odd instructions that will not divide evenly with 4. Like your 2 byte ADD instructions (11CCs) and your two byte inc/dec instructions (6CCs).

I use this one! http://www.ticalc.org/archives/files/fileinfo/427/42722.html

I know this is off-topic, but Since when ticalc.org accepts anything else than zip files in the non-Windows/Mac/anything other than TI-81 directories? O.o

The clock cycle information you guys are viewing isnt completely accurate. Depending on wether the register value has to be prefetched or not will actually increase the number of clocks. The links Ive looked over on this post dont mention this, but the values that they give are actually based off of the best possible scenario. Its been a while, and I could be wrong though. But if you really need to know the exact times of the instructions I would do some research on the prefetch. You probably dont need to get it that exact though