Apache Virtualhosts file for creating dynamic virtual hosts

httpd-vhosts.conf

#
# Virtual Hosts
#
# If you want to maintain multiple domains/hostnames on your
# machine you can setup VirtualHost containers for them. Most configurations
# use only name-based virtual hosts so the server doesn't need to worry about
# IP addresses. This is indicated by the asterisks in the directives below.
#
# Please see the documentation at 
# <URL:http:/httpd.apache.org/docs/2.2/vhosts/>
# for further details before you try to setup virtual hosts.
#
# You may use the command line option '-S' to verify your virtual host
# configuration.

NameVirtualHost *:80

<Directory "/Users/robert/Sites">
    Options ExecCGI Indexes MultiViews FollowSymLinks Includes
    AllowOverride All
    Order allow,deny
    Allow from all

    DirectoryIndex index.php
    UseCanonicalName off
</Directory>

# Flow installations mapped to *.flow.dev
<VirtualHost *:80>
    ServerName local.dev
    ServerAlias *.dev
    VirtualDocumentRoot /Users/robert/Sites/%-2+/Web
		SetEnv FLOW_CONTEXT Development
</VirtualHost>

<VirtualHost *:80>
    ServerName local.prod
    ServerAlias *.prod
    VirtualDocumentRoot /Users/robert/Sites/%-2+/Web
		SetEnv FLOW_CONTEXT Production
</VirtualHost>

I generally followed these instructions for dnsmasq on OSX:
http://inspirix.wikispaces.com/dnsmasq-on-OSX

For dnsmasq.conf you need to add these two lines:

address=/.dev/127.0.0.1
address=/.prod/127.0.0.1

Then for the resolving part, don't change the DNS settings in Network Preference Pane but instead create a directory /etc/resolver and add a file "dev" with the following content:

nameserver 127.0.0.1

That should be it.

@robertlemke: Thank you, very helpful!

For those who are blind like me, make sure to replace the directory paths in "VirtualDocumentRoot" and in the <Directory "..."> part!