Lightroom, Aperture and iPhoto
Before Lightroom came out (even as a beta) I started using Aperture on my MacBook Pro (work machine) and my Dual 2Ghz PowerMac G5 (primary home machine) to manage my photos and do any RAW adjustments on the files I shot with my Canon 20D. Before that, I had used iPhoto to manage and organize my photos including ordering 4x6 or 5x7 prints. In fact, my wife loves using iPhoto (and later Aperture) to order prints because as much as I love printing on my Epson R2400 or my Epson 3800, I don't like printing 80 4x6 prints of 50 different pictures. It's just too time consuming not to mention it somehow feels silly to print a 4x6 on a printer that can handle much larger prints.
Anyway, where I'm going with this is that I really liked (and still do) Aperture's organization features, the Light Table feature the way they handle "virtual" copies of files (one for B&W, one for color, etc) but the thing I liked the most was printing books and ordering prints. Again, it came down (like many things in my house) to what my wife (Chris) liked. However, what I didn't like about Aperture was the performance on my Dual 2Ghz G5. It was slow to do any kind of serious adjustments. Making similar adjustments in ACR or Lightroom are much faster (or at least feel that way - I haven't done any formal time tests).
So when Lightroom came out in beta, I started using both. When Lightroom 1.0 shipped, I started to just put my new photos into Lightroom (I don't want to use 2 apps to manage my photos if I can help it) which was great, but I suddenly lost the easy way to order prints and books. But there's a cool thing you can do with Lightroom and Aperture or iPhoto if you're on a Mac OS X computer.
I created a couple of Automator applications for Aperture and iPhoto that will import any files that show up in one of two folders on my Mac and then import them into either application into a project folder (Aperture) or photo album (iPhoto) and then delete the files that were placed into those temp folders. Next, I set up a couple of Export presets in Lightroom that will export selected photos and copy (that's important) those files to one of those two folders and then run one of the two Automator actions. This makes my life easier now because I can do my organizing and photo developing in Lightroom yet still get my selected photos into either Aperture or iPhoto so I can order books or prints or use them in any one of the iLife apps that I use at home (iWeb for example) or Keynote at work.
If you'd like to do this, first download one (or both) of the Automator actions. Download the one for Aperture here and the one for iPhoto here. Put the file(s) you downloaded into the following folder on your Mac.
~username/Library/Application Support/Adobe/Lightroom/Export Actions
If you use the Automator files I've provided, be sure to have a project or a photo album called "Lightroom" in your app of choice or edit the Automator action to use the album name you want.
Next, launch Lightroom and create a couple (or just one) new Export Presets. To do this, select a photo or photos and then go to the File menu and choose Export... (or press Cmd-Shift-E). In the dialog box that appears, you'll create a new preset. Choose a folder (any folder) where you want the files to be copied to, adjust your settings to your liking and then at the bottom of the dialog, in the Post-Processing section from the drop down menu choose one of the Automator actions. This tells Lightroom to do that action (whatever it is) once all of the files have been copied and processed to the new location. You can save this export preset as well for easier use in the future.
So there you have it. A great way to get any photos out of Lightroom and into Aperture or iPhoto!