[Click] Recommendation for network TAPs

[Latency Buster]

In addition to traffic shaping, I plan to use click for doing traffic
correlation. I am being questioned regarding the nature of taps and
what's a good place to purchase them would be.

So, here goes my question to the click community: What kind of
networks taps (optical and copper) would you folks recommend that does
faithful packet mirroring and is extremely reliable? We would be
tapping from our IT infrastructure and reliability is a pretty high
concern here.

Thanks!