Update 10/2011:
- new 1.5 version
- tested under debian squeeze...and it works
- add 'wanpipe'option. it should be useful for people that are using sangoma's cards
- add some more fool-proof checks


Original text from 08/2011:

This asterisk installation helper (aih) *should* help you install asterisk (+ dahdi linux/tools, libpri...) from source. For now you can choose between versions 1.6.2.x and 1.8.x and all the latest stable libpri, dahdi-linux and dahdi-tools. Before compiling dahdi-linux it will offer you an  option to compile it w/ oslec echo canceller. Script has somewhat fool-proof logic, so it won't allow you to try installing 1.6.2.x and 1.8.x at the same time, if you select the whole 'pack', it will compile them in proper order i.e. libpri -> dahdi-linux -> dahdi-tools -> asterisk and so on. Script, again, *should* run on debian and centos (like) os's. tried myself on debian 5.0.7 and centos5 few test installations and it all went fine. 

most importantly, you still have to know what you're doing especially when it comes to selecting proper versions for the software mentioned above!!! 

anyway...download from here...untar it and run it (as root)  ;)