Preview has an Import function that allows you to grab images from various sources. If you choose, in Preview, File > Import Image while your iPhone is plugged in, will open a new window with all of the photos on your iPhone camera roll. You can then select photos and choose Import and the photos will open in Preview, thus allowing you to save or export photos from your iPhone without using iPhoto or Image Capture.
[kirkmc adds: I don't have an iPhone, so I can't test this, but it makes sense...]
Mac OS X Hints
http://hints.macworld.com/article.php?story=200808132042190