My brother-in-law was married this weekend in Sacramento, CA. While Julie was a bridesmaid, I lacked an official capacity in the ceremony. Seeing this as an opportunity, I assigned myself the role of second photographer for the wedding. The primary photographer was a friend and roommate of the couple who actually has a degree in photography. He (Angel) seemed genuinely pleased to have me help out and fill in the gaps.
The lighting for the wedding as a whole was basically horrible. The ceremony was outdoors at high noon in the hot Sacramento sun. I only took a few photos during the ceremony, but was unfortunately too far away for my flash to provide a decent fill. I don't know if Angel was able to fare much better. He was a bit closer, but I haven't seen his photos yet. Here's a typical ceremony photo, complete with dark shadows under the eyes and face.

Inside the reception hall the light was worse. It was a large dark hall with 20' high ceilings and lit with many (but not enough) incandescent lights. Bounce flash was clearly impossible, but to top it off, the back of the hall had a large window where daylight spilled into the room. Not enough to overpower the foreground, but enough so that when I color-corrected my flash for the incandescent light, the background was still often blue. I managed to put my new 30mm f1.4 lens to good use and took most of the photos with it at around f1.4 - f2.8 at ISO 800 and 1600 with flash.

The best lighting was in the prep rooms and a waiting room that were used between the activities. Large windows and a little bit of bounced flash gave some very nice results. One of my favorite shots of the entire weekend is below. It was taken post-ceremony and pre-reception while waiting for the large formal photos.

Overall, it was a great learning experience. Knowing that whatever photos I took were only going to complement the actual photographer's photos took a lot of the pressure off. Sometimes I screwed up, sometimes I got a great photo. I managed to use my macro lens, Lensbaby, gels, and try a little off-camera flash in a real-world situation. It wasn't easy, but it improved my photography skills.
View my favorite photos from the wedding on Flickr.