If it's mathies and CS guys, I would probably tailor a speech to something that would involve both of their skill sets and remind us of their mutual importance.
For example, the development of public-key cryptography is a good example of how arcane mathematical techniques were used to create a technology which underlies virtually all on-line secure communications today.
http://www.ics.uci.edu/~ics54/doc/secur ... story.html
The Diffie-Hellman public-key cryptography method also has a political history: for quite a while, the United States attempted to restrict export of any software which used keys longer than 40 bits, so there were 128-bit "domestic" versions of Netscape and 40-bit "export" versions of Netscape, in order to comply with US federal regulations. This technology allowed communications privacy on a widespread level, and that frightens governments. At a time when Wikileaks is dominating the headlines, this is relevant.
Anyone can talk about the Internet, but most of the public doesn't even know what public-key cryptography is. If you're talking to mathies and CS guys, I would probably go for something like that.