EDIT: .data and .code macros instead of defining sections (3.2.2 in documentation).

Ive been on and off working on a little opengl project for a while now, usually when wow servers are down or something :p. And im starting to reach a point where code management is becoming a priority.

The ways i know are to create dynamic link libraries but these don't allow you to share variables easily. To create inc files with procedures them and use local/virtual variables but all global variables all have to be in the main file. Or to have a .data include and a .code include for your procedures and include them in the .code and .data sections of your app.

Im currently using the last method which works, but i really want to not have the data and code in separate files. Ideally i'd just like to define another .code section and have the assembler just append all the .code sections together (same with .data) but that comes up with the error "out of memory".

Any ideas on code management in fasm?

These macro's are defined in WIN32AX.INC and as far as i can tell, they are only to provide an easy way to declare a section.
I looks like multilple sections of the same type can be defined, but i dont think that fasm will group them together (like a linker does) so your file size will probably increase due to each sections alignment width.
If i am wrong, please kick me in the nuts...

Exactly there is no such grouping. And you don't only have to account for the alignment but for the extra space required to define the section inside the PE too.

The best way I've found thus far is to create object files and link them together. Linkers have a policy used to join sections of same, or similar names. Matt Pietrek explains briefly (just past Figure 2). This allows functionality to be encapsulated within a single source file (and typically a definition of the interface - include file).

Better tools to navigate large sources is required to realize the FASM single source file dream, imho.