this may be more info than most care to read.
i used to design wheels for both an oem wheel supplier and manufacturer. the general rule of thumb, at least for oem car wheels i worked on, is to add 2 to the wheel diameter and you have your weight. example: you have 17x6 wheels. take 17 add 2 and the wheel weighs 19 pounds. this seemed like an optimum weight that would meet the oem requirements yet still be strong enough to pass impact testing. for larger wheels like 20" you should add 3 or 4. there are many variables to determine weight. the style of the wheel and whether it has a button cap or large cap covering the lugs can greatly affect the weight. we used this simple calculation to give us a ball park #.
chrome wheels are typically 2 pounds heavier than the same wheel that is painted or polished. the reason is that the wheels are copper plated, then chromed. even though the plating is thin, both metals are quite heavy.
also, the wider the wheel the more weight. a 8" wide wheel vs. 7" wide will add 1/4 to 1/2 pound.
my point is that if you are unsure if a wheel is "too heavy" just use this simple calculation. if the wheel is few pounds more than the diameter it is a reasonably light wheel.
truck wheels are beefier to withstand higher loads. you could add 5 or even higher to get the approximate weight.
oem wheels are usually much lighter than "california" aftermarket wheels. you know, the ugly wheels with teddy bears and flames. the main reason is cafe standards, second is cost savings. aluminum is $.80/lb. aftermarket wheels do not have to meet cafe standards and have a much bigger profit margin. so they can "afford" to make a heavier wheel. thus they do not go to extreme lengths to lighten a wheel by 2/10ths of a pound like oem's yet still be robust enough to pass impact testing. however, with the aftermarket trend going towards lightweight racing type wheels this should change. racing style wheels should be on par with oem wheel weights or even less.
remember, these are just guidelines. if you want specific weights, then call the manufacturer.
if you really want super lightweight wheels, get a thin 5 spoke. they usually seem to be the lightest vs 6 or 7 spoke. defineately stay away from 3 spokes as they are inherintly heavy-just take my word for it. to get every last ounce of weight out get a wheel that has been rollformed(the rim is spun). this can reduce the weight by a pound. speedline (italy) specializes in super lightweight, yet strong wheels, many of which are rollformed. the aftermarket wheels are named speedline corse.
then of course there are magnesium wheels. mg is 1/3 lighter yet 1/3 stronger than aluminum. however, it is more expensive per lb and dangerous to cast. my boss had c5 mg wheels given to him for his c5. nice!
hope this helps, canuck