Arranging possible speaking opportunities takes considerable effort and involves a long lead time. In most instances, you must be in contact with the conference organizers at least nine to ten months in advance of the show. You may even find that a sponsorship is required to be considered as a possible presenter.
First, do your research regarding relevant conferences that are being planned in your area in the months ahead. The website of the event organizer or of the conference itself is often a good place to start looking for information. Contact the organizers to find out their needs and application requirements for possible speakers.
Also, consider other venues in addition to trade shows focusing on Linux and open source. For example, you could offer your services as a speaker to human resources or computer training communities.
The key to successful participation is similar to pitching to the news media. You must understand your audience, you must have a compelling topic, and you must be ready and willing to impart your knowledge and experience of the industry. Most importantly, your presentation has to teach something to someone, and not just be a commercial for your organization or Linux. Give the audience the satisfaction of having really learned something from your presentation, and show organizers will want to have you as a presenter at their next show.