I have a basic understanding of LaTeX. But I would like to learn more through LaTeX examples or real world usage (probably commented). Where can such be found?
The sources of a lot of the examples from the LaTeX books can be found here: Examples from CTAN
It's hard to answer this question without knowing what "real world" you inhabit. If you're looking for math examples, then the
mathmode documentation is essential. (It should be part of your TeX distribution.) The LaTeX Companion 3rd Edition by F. Mittelbach, M. Goosens, J. Braams, D. Carlisle and C. Rowley (Addison Wesley) is full of example code with extremely good explanations. For examples of drwawing with
pgf/tikz, see the here. Maybe others can add more suggestions to this list.
The best way to learn LaTeX is by using it. The "real world" you are presumably interested in is the world of things you actually want LaTeX to do for you. And if you want to learn about those things, try them!
The already mentioned link includes several excellent resources (the LaTeX wikibook, the not so short introduction...) but be selective! There is a lot to learn, so don't just sit down to read a LaTeX book cover-to-cover. Not at first. Try to do something (typeset an article, draw a picture in TikZ, write a letter...) in LaTeX and when you get stuck, search out the relevant parts of the above mentioned resources.
I think the sort of thing you are requesting (commented source code examples?) will be of limited use, unless you want to do more or less exactly the same thing as what that code does. You're much better off trying to write your own code and learning that way.
Edit: Another useful list of resources (There's a lot of overlap with the other link...)