I know a lot of people that has been trying to share their internet over WLAN, or just to set up a temorary WLAN to play some LAN games on the train, with Ubuntu and NM (Network Manager) 0.7, which comes with Ubuntu 8.10 Intrepid Ibex.
The thing is that NM has been able to create WLAN for some time now, but untill no it has not been that functional. Now you can share your primary internet connection (detected by NM) over WLAN with just a few clicks.
But there is one thing that depends on it.
By some reason, which I dont know a small package needed to actually share your internet or creating a network, isn't installed by default. But thats easy! Just install dnsmasq-base and you are good to go.
Install it ither by the command line;
$ sudo apt-get install dnsmasq-base
Or search and install it using Synapic or Adapt.
Now you are able to create a Wireless network connection using Network Manager 0.7. Just klick on the network icon in the notify-area.
Cheers and hapy new year!