Some do it more formally than others. Paladin Capital has an explicit focus on "homeland security issues and needs." Chart Venture Partners in New York does that sort of deal, or did when I last worked with them.
On the less-formal side, Novak-Biddle Venture Partners in the DC area is also quite friendly to what I call "dual use" deals, where there might be a government play in addition to the commercial one. From a founder's perspective, they're good folks, too.