This is a selection of random links I've found useful at one time or another. I haven't read every word and no real endorsement is implied by being included in this list, but it might be useful because sometimes links pages are easier than google.
24p.com - extensive HD info
broadcasttech.net - includes error codes for old Sony VTRs
martindalecenter.com - calculators for bitrate, bandwidth, viewing distance & all sorts of other things
zytrax.com - comprehensive techinfo links page
broadcastpapers.com - white paper repository