If you are looking to put together some sort of talk for one of the open space sessions at an Unconference, remember to keep it short, use the live web rather than slides if possible and create opportunities for engaging in conversation.  The biggest problem with all presentations (at conferences or in small meetings) is that they are more about talking to/at rather than talking with.  That does not mean to say that the presentation format is dead per se, as there are many useful instances where presenting longer form 'stories' are key to informing the audience on a given topic.  The difference is that we should no longer presume the presenter to be the sole authority on a given subject matter - all participants should be given respect for the potential value they can contribute.