Digidesign's AIR Phaser is a plug-in available in the newest version of Pro Tools. Pro Tools 8 features a whole line of these AIR plug-ins, which stands for Advanced Instrument Research. They all have a similar look and are all free! Like all of the AIR plug-ins, the AIR Phaser plug-in installs automatically when you install Pro Tools 8, so you don't have to worry about any other steps to install this plug-in beyond installing the main software for Pro Tools 8. The interface of the plug-in is to the point and is generally very easy to follow. It's got main parameters for rate, depth, feedback, and mix, as well as a section entitled 'phaser' which has poles parameter, which gives you four different steps to choose from, as well as a center parameter which allows you to adjust the frequency. There is also an LFO section with parameters for waveform, and left/phase phase. Lastly, there is a low cut knob with an adjustable frequency. I don't believe that they make manuals for these plug-ins, but you really don't need one anyway.
Having just upgraded at home to Pro Tools 8, I'm running the Digidesign AIR Phaser plug-in on a Mac Book Pro that has a 2.2 Ghz Intel Core 2 Duo processor and 4 GB of RAM. I run Pro Tools with a Digi 002R audio interface or the Digidesign Micro Box for when I'm not at home. So far in the relatively small amount of time that I've been using the AIR Phaser plug-in, it hasn't even come close to affecting my system's performance. I've only had a need to use one or two of them within a single session, so it isn't like I'm trying to max it out. However, I think that as long as you have a system where you can currently run plug-ins and Pro Tools comfortably, this one shouldn't be a problem.
Let me start off by reiterating the fact that this plug-in comes free with Pro Tools 8! Moving forward with this in mind, the Digidesign AIR Phaser is a very useful plug-in to have in your arsenal. It won't do the heavy damage that phaser plug-ins like the Eventide Instant Phaser or the Soundtoys Phase Mistress will do, but for a freebee it sure sounds good and offers up a good amount of versatility. If you've got Pro Tools 8 I'd highly encourage you to get in there and play with this one for a bit to see if it is something that could be useful for you. If you don't have Pro Tools 8, you don't have any way to get this plug-in, so I'd recommend upgrading!