I always keep a 72mm u/v filter on my lens, just for protection. I've also found circular polarizers to be handy for lots of outdoor shooting situations.(posted 9132 days ago)As for tripods, Bogen has some reasonably inexpensive ($300ish) tripods/fluid-head combos that, while not amazing, do a very competant job with the XL1's weight.
If you haven't already gotten one, you'll probably want to consider getting xlr adapter for when you inevitably go with a mic other than the omni that comes with the camera.
Enjoy your new XL1--it's a terrific tool.