I see many cakes on here with beautiful, perfect fondant letting. Are they using letter molds? If so, does anyone know where I can find them? (Im not talking about using cutters)
If they arent using molds, how are they making the letters SO perfect every time?

I think most are using tappit molds or a cricut machine.

I know you said you're not asking about cutters, but a lot of people get beautiful results with the tappits. Here's a great tutorial that shows you the "trick" necessary to cutting perfect letters.

I have one set of funky letters that I use - but if I need particular font, like Toy Story, or Porsche (see my cakes) - I'll print out the letters I need in the size I need on the computer - then I cut those letters out - then I lay them over rolled fondant or gumpaste and cut them out with an exacto knife. Arduous?? Yes - but it gets the letters I want. A little tip - when using an exacto knife to cut things out, try and use one continuous cut without lifting your knife.

Gumpaste using tappits or clixsticks

I agree with others, most would be using tappits, clickstix or a cricut machine. Thats not to say that you can't get molds though, so some people may be using molds - like these for example: http://www.firstimpressionsmolds.com/alphabets.aspx

I bought a couple of the firstimpressions alphabet molds, but what a pain! They are completely impossible (for me anyway) to get the letters to release without breaking/distorting. Plus it seems to take forever to get the fondant/gumpaste into the tiny cavities properly. I suspect their 'baby block' letters would work well, but as for the rest! Perhaps I'm just clueless to the 'trick', but I've never actually been able to make a whole word out of them, so have given up. It's SO much easier to use tappits.

Clikstix, Tappits, Cricut, Tracing, or pin prick method My advice.....disown the word perfect from your vocab when caking LOL

Did you try putting them into the freezer for awhile before taking them out of the mold???

Oh yes, you could also try chocolate/confectioners coating letter and number molds.  Easy peasy also.