Do you have some knowledge you want to share? Maybe you just discovered a tool which makes your life easier, or maybe you just discovered something ugly and want to warn others before they face the same thing. Possibly you want to share a success story, or maybe a failure story. Someone wants to hear it.
But where do you find an audience? There are plenty of venues in search of content, it is a matter of matching your information to the audience.
Technology and security groups are everywhere and most are frequently seeking presenters. For security issues, local NAISG chapters around the world are a good option. Depending on the specifics, Linux user groups are a good audience for talks on Linux and other Open Source projects, including integrating them into production environments. You may also be able to find a group through Culminis. Join the mail lists of prospective groups and contact the leaders, many will work with you to help you get your message heard.
Is it something that would work well in print? Think about the print and online resources you read, if there is one where you would expect to see an article like yours- ask them about submissions.
Want a bigger audience? Everyone knows about the big conferences like BlackHat and DefCon- and most are intimidated by the thought of presenting at them. There are plenty of smaller events which are more likely to work with you in tuning your presentation and proposal- Shmoocon and SOURCE Boston to name two.