In which order do you recommend I try to learn the packages: HList ->
AspectAG -> SyntaxMacros?

I think HList -> TTTAS -> AspectAG -> SyntaxMacros is the best.

I tried to read the SyntaxMacros-paper but had a hard time
understanding which parts belonged to the package and which parts
belonged to your new mini-language. Do you got the mini-language as a
separate download?

The examples folder in the package has the implementation of the mini-language and its extension.

You mention in the paper that the source of the paper is in literate
Haskell and that the code is available but I can't find it at the
wiki. I found some code (Expr.hs, Main.hs) in the examples-folder in
the packages source code (SyntaxMacrox-0.1.tar.gz) but it doesn't seem
to match 1:1 to the code in the paper (couldn't for example find
extSpecChars in the paper or updateFinalEnv in the source code).

The package includes the code of the paper:

- Language.Grammars.Grammar has the grammar representation (section 3.1)
- Language.Grammars.SyntaxMacros has the code of the syntax macros library (section 3.3)
- The mini-language is in the examples folder, as I said before. Main.hs has the code of the first figures and Expr.hs has the code of the semantics definitions and redefinitons.
- updateFinalEnv and the other functions and datatypes showed in section 3.2 are included in the package TTTAS.
- extSpecChars and extKeywordsTxt are used to extend the scanner. That's not explained in the paper :-(