With years of measurements from the NBA draft combine, there's now a plethora of information of NBA player beyond the typical team listed height, which are often inflated. Measurements included here are height without shoes, height with shoes, wingspan, and standing reach, as well as the height listed in basketballreference. The average measurement for a position is based on minutes played  if there's a 6' 10" player with 1000 minutes and a 6' 8" player with 500, the average is 6' 9.3"  and the position used is from basketballreference. That system for position is far from perfect, but no system is, especially since positions have become so fluid.
Results
The results are shown in the table below. Shifted measurements have minutes at each position balanced so they all have the same total amount (i.e. if centers have less minutes, some power forward minutes are moved there.) OLS regression was used to fill in the missing data where each set of measurements has two or three equations based on the available information (to predict standing reach, wingspan is valuable information, but if that's not available move on to the next equation.)
Average measurements
Position

Height without
shoes

Height with shoes

Bref listed height

Wingspan

Standing reach

PG

6’ 1.2”

6’ 2.3”

6’ 1.9”

6’ 5.3”

8’ 1.6”

SG

6’ 3.8”

6’ 5.0”

6’ 4.7”

6’ 7.9”

8’ 4.8”

SF

6’ 6.6”

6’ 7.9”

6’ 7.6”

6’ 11.0”

8’ 8.8”

PF

6’ 7.7”

6’ 8.9”

6’ 9.2”

7’ 1.1”

8’ 11.1”

C

6’ 9.8”

6’ 11.1”

6’ 10.8”

7’ 3.3”

9’ 1.7”

Position shifted average measurements
Position

Height without
shoes

Height with shoes

Bref listed height

Wingspan

Standing reach

PG

6’ 1.3”

6’ 2.4”

6’ 2.0”

6’ 5.4”

8’ 1.7”

SG

6’ 3.8”

6’ 5.0”

6’ 4.7”

6’ 7.9”

8’ 4.8”

SF

6’ 6.5”

6’ 7.8”

6’ 7.5”

6’ 10.8”

8’ 8.6”

PF

6’ 7.6”

6’ 8.8”

6’ 9.0”

7’ 1.0”

8’ 10.9”

C

6’ 9.6”

6’ 10.9”

6’ 10.7”

7’ 3.1”

9’ 1.4”

Not every player has a draft combine measurement, and for those regression equations were created to fill in the gaps. The results are only slightly different, but it is important to see if the results even change, and the equations can be used to estimate measurements of other players. One random find was that players close to sevenfeet tall are no more likely to inflate their height than other players. I thought there'd be a whole number bias, but I suppose not.
Average measurements, missing data regressed
Position

Height without shoes

Wingspan

Standing reach

PG

6’ 1.1”

6’ 5.3”

8’ 1.2”

SG

6’ 3.8”

6’ 8.1”

8’ 4.8”

SF

6’ 6.5”

6’ 11,0”

8’ 8.7”

PF

6’ 7.9”

7’ 1.3”

8’ 11.2”

C

6’ 9.9”

7’ 3.2”

9’ 1.7”

Position shifted average measurements, missing data regressed
Position

Height without
shoes

Wingspan

Standing reach

PG

6’ 1.2”

6’ 5.4”

8’ 1.3”

SG

6’ 3.8”

6’ 8.1”

8’ 4.8”

SF

6’ 6.4”

6’ 10.9”

8’ 8.5”

PF

6’ 7.8”

7’ 1.1”

8’ 11.0”

C

6’ 9.7”

7’ 3.0”

9’ 1.4”

Draft implications
When evaluating a player's size, looking at the average measure at each position makes it more of a fair game. Too often guys are derided for not being true centers, for instance, because they're not sevenfeet tall, but that's the norm. Nerlens Noel is the top prospect in the draft, and some fear he's too small for a center. He was 6' 10" without shoes, almost perfectly average, with a slightly above average wingspan of 7' 3.75" and standing reach 9' 2". Although the weight is a concern in post defense, he's nearly the league average measurements for a center.
In the case of Trey Burke, measurements mean the difference between being taken second and sixth. Without shoes, he was a paltry 5' 11.75", sliding under the Mendoza line for NBA player height, but looking at his effective size  you don't play basketball with the top of your head; you play it with your hands  he's actually fine. Both his wingspan and standing reach are about average at 6' 5.5" and 8' 1.5", respectively.
For players who are undersized, Anthony Bennett is a shade under the averages for a power forward, from the measurements we have, and Cody Zeller's Trex arms are a killer. His height was above average, 6' 10.75" without shoes and over 7' with them, but his wingspan was slightly below average for a small forward  6' 10.75", as having a wingspan the same as your height is actually rare for an NBA player. Consequently, his standing reach is below average for even a power forward at 8' 10". Speaking of short arms, Kelly Olynyk actually has a smaller wingspan than height without shoes  6' 9.75" to 6' 10.75", but at least his standing reach is 9'.
For some better news, Otto Porter is a big wing. His size is more similar to a power forward's  a wingspan of 7' 1.5" and a standing reach of 8' 9.5", along with a height without shoes of 6' 7.5". If a team wants to go with a smallball lineup, you can definitely get away with Porter as the "four" there. Steven Adams appears to have good size for a center, as his standing reach is almost exactly average at 9' 1.5", and his wingspan is 7' 4.5". But it's Rudy Gorbert who steals the headlines. He has a Condorlike wingspan of 7' 8.5", largest in recorded draft combine history, and a standing reach of 9' 7", only bested by the Russian giant Pavel Podkolzine. He's also the only guy in the 2013 draft measured at over sevenfeet without his shoes, which is actually rare. Athletically, he's not up to par, but strangely enough his speed and jumping measurements were very similar to Brendan Haywood's, who had a long career, and perhaps Gorbert can be the next Shawn Bradley  and not the next Pavel Podkolzine.
As a last note, NBA projections typically use a player's listed height and ignore wingspan and standing reach because there's more data available that way. Looking at average measurements perhaps one can adjust a player's height based on his wingspan and standing reach to an effective height. For example, Cody Zeller's measurements are somewhere in between a SF and a PF, and the average listed height between those two positions is 6' 8.3", depending on whether or not you use shifted measurements. Using 6' 8" instead of his listed height of 7' could dramatically change his projected impact.