There is something called IpInfo or something like that in the download section too. I think similar to this one it's really made for just the local machine, but on the plus side it gives you the mac-address(s) and shows you all your local ip's for each adapter you've got. Comes with the source code so I imagine with a little work you could get it to scour a local network.

>I don't know about all users, but the current machine's ip can be retrieved by:
>
>http://www.levelextreme.com/wconnect/wc.dll?FournierTransformation~2,84,14,7778
>
>>Hi,
>>
>>how to get all user ip address on the networks
>>
>>regards