I was wondering if there are any ways to get certified in TeX/LaTeX? This would be useful, e.g., for providing a way of quantifying the expertise someone has with TeX, LaTeX or other TeX flavors.
AFAIK there is no official certificate. You may get one from a lecturer or a school when you participated in a course.
It would be nice if there was something comparable to the Linux certificate, with certain levels such as:
Well, there should probably be a few more levels.
It's nothing official, but you could point people to your profile here at tex.sx. Reputation is *TeX knowledge quantified, if you want to put it this way. You could use your flair as well or point to the percentile your belong to, which is in your case currently "top 16% this week", I'm "top 5% overall", egreg is "top 0.09% overall" = No.1. You find this information in the reputation box on your profile summary. Here's your flair:
One way or the other, I'm sure people would believe egreg that he knows his way around *TeX if he showed them his profile/flair:
Going further (and further abusing egreg as an example), tags actually provide an overview of a user's fields of expertise, even though these are also highly dependent on what users ask about. The same applies for tag badges (listed before the regular badges, distinguishable through the different background color).
Stack Overflow actually took this concept a step further with Stack Overflow Careers, where users can create a profile combining personal information with stats from their SO profile.
While tex.sx is certainly not yet as big in the *TeX world as SO seems to be in the programming world, I have a feeling it's steadily growing in importance, as we are gaining more and more highly knowledgeable and well-known experts as members and as regular contributors.
Responding to some of the comments:
Reputation is not a negative indicator of knowledge, i.e. low rep doesn't mean a person is not knowledgeable; but beyond a certain amount of rep (perhaps 10k or 20k at the moment) you can be quite confident that a user has a thorough understanding of some fields and principles of the *TeX world. Of course activity plays an important role, and so does the popularity of the topic you're answering about, but these may be regarded cornerstones of this "certification": "Normal" certificates may require you to spend a certain number of hours in class or on a project (= activity on tex.sx); the relative popularity of a certain topic reflects the (admittedly potentially irrational) relevance that the tex.sx community assigns to that topic. There still is a lot of inaccuracy and randomness going on -- I wouldn't think Cthulu worshipping madmen play a major role in daily *TeXing, as the rep gained from that question might imply -- but isn't that the case with certificates and standardized tests as well (I think that's the point that @Brent was making)?