Greg(Solidguy), a few tips (& some repetitions)
1. As others have said make sure prepared, but also remember that you are being asked to deliver a speech, so they (the organisers) have already registered the fact that you know your stuff... you need to remember that yourself!
2. If you get a chance practice (no more than 3 times) in front of mirror. Why? Because when you speak out aloud (again as has been pointed out) you will think that your voice sounds different (and sometimes it does). I deliver presentations all the time as part of my job and i can tell you that my presentation voice is very different to my conversation voice. Why no more than 3 times, well one it gets boring and two you may become hyper critical of yourself and your style. The first time will be a shock and the second and third times you can concentrate somewhat on delivery... ensuring as far as you can not to be deliver in a monotone, but change emphasis when you are coming to an important point in your presentation, but also to ensure that you do not speak too fast and/or mumble because you are nervous.
Before i was let loose in court some aeons ago we had formal presentation advice sessions and we were videoed.... and it was embarrassing. But the playback highlighted some very good points (i'm not suggesting that you video yourself (doesn't sound like you have the time anyway)) but if the organisers of the conference do video the proceedings, get a copy and watch yourself again - but again, not to be hyper critical, but just to see how you are in that situation, because i suspect that you will be asked to do this again and again and you will want to improve. Even better if you can get someone whose opinion you trust and value to watch it with you and listen to what they have to say. Needless to say when i watched my video and received the constructive criticism, i rarely ever made the same mistakes again... i had the video as backdrop to continually haunt me
3. The practice will also help you time yourself as you will have been given an allotted time frame.
4. On Friday before the presentation, focus on breathing.... Sounds silly be you will be surprised how when you are nervous, your breathing quickens or you hold your breath and that directly affects the way you deliver your speech.. so even while giving the presentation remember to breathe
5. Penultimate point - nerves are a good thing, providing you control them. If you are not nervous before a presentation, then most likely it will be bad in some way shape or form... bitter experience has taught me that!!!!
6. Finally... and this really sounds stupid... but it's not.... TRY YOU BEST TO ENJOY IT! If you can manage to relax.. even just a little bit and dissipate some nerves, enough to allow you to give a storming presentation!!!!