It's the one you all want to ask. What does the hoarder bring with her when she travels?
Here's a secret: I'm the lightest packer I know. Below is a picture of my gear for this now 19-day trip:
The paperback is there both for scale and because it was my reading material. (Well, ok, I did bring another book, but I finished it, so it's stored in the trunk now).
I pack lightly because I like to be able to carry all my gear on my own if I need to. For this trip, I did have to bring more things than I would for a plane trip. The trunk of my little car is actually full--we have a box of snacks, a case of water, clothes and such for four people (everyone has a little case similar to mine), DH wanted to bring his telescope and tripod and since there was room, we tossed it in. We have the laptop, tons of maps and AAA guidebooks, toys for the kids and an ice chest. Still, we could have left about a third of the extras at home and still had a great trip. The telescope was super cool at Mt. Rushmore, but we would have been amazed without it. The snacks and water saved us money and time, as did the ice chest. Maps are a necessity, although we did have a GPS along with us and it came in handy for calculating trip leg times (it was accurate to within three minutes for our leg from Utah to Oregon).
If you too want to travel light, the best resource I know is the Travel Lite FAQ by Lani Teshima. She's been on the internet and writing about travel for a couple of decades now, and although the date on the FAQ is a bit old, the information is still very useful.