It's an interesting question, depending on how much of a Steelers homer you might be..LOL. Seriously though, there are a number of names that I can think of off the top of my head of players who don't get the respect they deserve among active players.
Heath Miller - long known to Steeler fans as one of the best in the business, but due to the nature of Steeler offenses, he just doesn't get the stats that other high profile tight ends do. Being in the AFC he is overshadowed especially by Antonio Gates and Dallas Clarke, both of whom are top notch. When Miller isn't in the game though, the offense suffers and his absence is noticeable. Something else that Heath does that both Gates and Clarke don't do nearly as well, is block! Miller has been money every year in all phases of his game. When he was down with that concussion in 2010 for a couple weeks the offense was noticeably less effective.
Rashard Mendenhall - Yeah I know he fumbled in the Super Bowl, but he was a big part of the offense all year. He rushed for 1,273 yds. and 13 Touchdowns in 2010. Sure there are players with more yds and more Touchdowns but I would argue that Rashard is as important to the Steelers as any running back in the NFL is to their team. His ability to be the power runner as well as the breakaway threat make him a unique commodity in the NFL.
Brett Keisel - Given the absence of Aaron Smith from the lineup the last couple years, Keisel has really been able to shine and take on more of a leadership role on and off the field. When he missed a few weeks with his hamstring, the defensive line missed him. Keisel is a good pass rusher while still being able to clog the lanes and help shut down the run. Is he the best DE in football, no, but he's well above average and when you talk about good players at his position his name rarely gets mentioned.