Software used:
  • Ubuntu 9.10 Karmic
  • Asterisk 1.4.30-rc2
  • libpri 1.4.10.2
  • dahdi drivers/tools 2.2.1
  • asterisk-gui 2.0
I settled for a 1.4 asterisk instead of 1.6 because I was having issues making asterisk-gui work with asterisk.

Now for the steps:

1. Install necessary prerequisites

sudo apt-get install linux-headers-$(uname -r) build-essential autoconf automake autotools-dev bison flex libncurses5-dev libssl-dev libtool subversion svn-buildpackage libxml2-dev
and create working folder 
sudo mkdir /usr/src/asterisk
sudo cd /usr/src/asterisk


2. Download necessary files
sudo wget http://downloads.asterisk.org/pub/telephony/asterisk/asterisk-1.4.30-rc2.tar.gz
sudo wget http://downloads.asterisk.org/pub/telephony/libpri/releases/libpri-1.4.10.2.tar.gz
sudo wget http://downloads.asterisk.org/pub/telephony/dahdi-linux-complete/releases/dahdi-linux-complete-2.2.1+2.2.1.tar.gz
sudo svn co http://svn.digium.com/svn/asterisk-gui/branches/2.0 asterisk-gui

3. Unpack the packages
sudo tar -xvf asterisk-1.4.30-rc2.tar.gz
sudo tar -xvf libpri-1.4.10.2.tar.gz
sudo tar -xvf dahdi-linux-complete-2.2.1+2.2.1.tar.gz


4. Install libpri
cd libpri-1.4.10.2
sudo make clean
sudo make
sudo make install

5. Install dahdi-linux
cd ..
cd dahdi-linux-complete-2.2.1+2.2.1
sudo make
sudo make install

6. Asterisk
cd ..
cd asterisk-1.4.30-rc2
sudo make clean
sudo ./configure
sudo make install
sudo make samples
sudo make config

7. Now for the web interface, Asterisk-GUI
cd ../asterisk-gui
sudo make clean
sudo ./configure
sudo make
sudo make install

8. Before you can finally use the web interface, you need to make some minor configuration. 
sudo vim /etc/asterisk/http.conf

and make the following changes:

[general]
enabled=yes
enablestatic=yes
bindaddr=0.0.0.0 or your IP Server
bindport=8088

9. Add the manager account
sudo vi /etc/asterisk/manager.conf

and make the following changes

[general]
enabled = yes
webenabled = yes
port = 5038
bindaddr = 0.0.0.0 or your IP Server

at the bottom of the file, add the following config:

[admin]
secret = yourpassword
read = system,call,log,verbose,command,agent,user,config
write = system,call,log,verbose,command,agent,config

10. Open the web interface at http://192.168.0.1:8088/asterisk/static/config/index.html

Screenshots:
System Status

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