1. AAXA P4 Pico Projector ($339)
This 80 lumen mini projector is LED based and will produce up to an 80 inch image. We wouldn't go that big probably, but you could. It also comes loaded with windows CE so you can run Office, Adobe Programs or other 3rd party applications right on it. And it's got built in stereo speakers and A/V and VGA input. We like how much you get with this single device, and if you're planning for it using it mainly for business the P4 is a strong competitor.
2. 3M MPRO150 ($318)
Shaped for use in the hand as well as on a flat surface, the MPRO150's got built-storage and support for your standard Microsoft Office products. Battery life is good at 120 minutes. Our only complaint is that it's light on lumens (15) so your presentations won't be quite as bright as products with larger light capacity.
3. ASUS P1 ($499)
Closer in shape and brightness to a traditional projector, the P1 provides 200 lumens of brightness and 1280 x 800 resolution. It can be set up a meter away from the projection and still project 40 inches across. We like the "auto keystone correction" which fixes that oddly shaped trapezoid you almost always get when setting up. And it's still under a pound, which meets our portability needs. Of course all that comes at a higher price than most of the small projectors we've seen.
4. Optoma Pico PK201 ($229.99)
Another palm-sized projector gives a little more light than the MPRO150 at 20 lumens. It's got USB, VGA, HDMI and video ports so you can view just about anything and tiny speaker for some audio (we suggest you bring a speaker that uses a headphone jack if you want better sound). The iPod kit and remote are additional sadly, but leaving them out keeps the price down and they are available.
5. MicroVision SHOWWX+ HDMI ($341.67)
We're not sure how but the SHOWWX uses lasers to create the image you're projecting and thus you never need to focus it. It's on the lower lumen end, but that's to be expected with a product billed as a compliment to the iPhone or iPad. It comes ready to use iProducts out of the box. The only downside is it isn't actually HD (despite the HDMI name it's only 848 x 480).