According to the Apache manual you can do the following; I did not modify the "hosts" file. Also see the documentation about mass virtual hosting. (see apache.org and search for terms)

# example

NameVirtualHost 111.22.33.44

<VirtualHost 111.22.33.44>
ServerName www.mysite1.com
ServerPath /web
DocumentRoot /web/mysite1
</VirtualHost>

<VirtualHost 111.22.33.44>
ServerName www.mysite2.com
ServerPath /web
DocumentRoot /web/mysite2
</VirtualHost>

<VirtualHost 111.22.33.44>
ServerName www.mysite3.com
ServerPath /web
DocumentRoot /web/mysite3
</VirtualHost>

# end example

It DOES work with the same IP for all three.

I also used a DNS Service (free for 5) to register the name servers @ http://www.zoneedit.com

Hope this helps.