Here are some of my favourite resources for designing presentations:
Garr Reynolds - Presentation Zen
The guru of presenting. Check out Garr's resources for organising, delivering and designing slides for your next presentation. Explore all of this site and read the blog every day. You too can become a presentation master.
Guy Kawasaki - 10-20-30 rule of presenting
Simple to remember yet powerful rule to apply when designing presentations.
Seth Godin - Tribes at TED
One of the worlds best marketers and a pretty good presenter. Watch and learn my friend.
The CommonCraft show
Not presentations per se, but a great use of stories and visuals to sell ideas.
Blair's presentation tip of the day
You and your story are your presentation just like the actor and his/her lines are the movie. Sound and lighting and backdrops and props (your slides and other multimedia wizardry) can either support or detract from you and your story. Use them wisely.