I am currently using Geany Text Editor (http://geany.uvena.de/) as my IDE (really, it can compile) for Allegro and other C++ coding in Linux. I find Geany much faster than Anjuta, Eclipse, MonoDevelop, etc with just the necessary features (Syntax Highlighting, Code Folding, Auto Completion, Symbol Lists, etc).
Here's how to get up and running with Allegro code on Geany:
1. Install Allegro and Geany from your Package Manager or build from source.
2. Run Geany and go to "Build" -> "Set Includes and Arguments" in the toolbar.
3. Use the following settings..
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Compile:
g++ -O0 -g3 -Wall -c -o"%e.o" "%f"
Build:
g++ -o"%e" ./%e.o `allegro-config --libs --static`
Execute:
"./%e"
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Copy the strings as it is, include the quotes.
Happy Compiling
g++ -o"%e" ./%e.o -lalleg -lm -lpthread -lXxf86vm -lXcursor -lXpm -lXext -lX11 -ldl
Why not:
g++ -o"%e" ./%e.o `allegro-config --libs --static` ?
Does that not work with Geany?
Also, this only works on linux, as you well know. And Geany is a cross-platform program, so the windows users who use it would be confused by your guide.
Thanks for the tip on Build string.
g++ -o"%e" ./%e.o `allegro-config --libs --static` indeed works. I've never thought of that before.
As for the cross-platform, the title says [Linux] first thing. I was just browsing the forums and didn't find anything Geany related so thought i'd make a post.
Darn... I fail... 
Consider putting this into allegro wiki too.
Whoa! Awesome!
I was looking for something like this for quite a while!
Was tired of using Eclipse and monodevelop and switched back to scite but I really missed an outline.
This rocks! Thank you very much!
SeigeLord: Great idea, added to wiki
http://wiki.allegro.cc/Geany
Christopher Bludau: Its a pleasure