Revive the waterproofing on your shell layers
Is it soggy season? Maintain your shell layers so they (hopefully) bead water like a new Ferrari.
There may be other products that do the same thing, but I'm gonna tell you ones that I'm familiar with: Nikwax Tech Wash and TX Direct.
First off, manage your expectations. Products like these are never going to get you back to “brand new” water beading, but they can usually stretch a few more years out of your favorite shell.
Don't go cheap and try to use just one; the Tech Wash and the TX Direct really do work better together. (These are packaged as a pair, that's a hint.) You can wash a lot of clothes with a couple of these bottles.
Frequency of using them mostly depends on how often you're out. If you're skiing 50+ days a year, you might want to do a wash cycle with this every two or three weeks during the season. If you're not out so much, maybe twice a winter should be fine.
Nikwax says the TX Direct is more for hard shell clothing. However, I've used it fairly successfully on soft shell pants and jackets. Your mileage may vary.
If you have other outerwear that you want to protect from the weather, like down jackets, gloves, fleece, etc., NikWax has a product for it. I haven't used these other ones so I won't comment on them, but they have a waterproofing product for just about everything you could imagine.
If you're wondering about nasty chemicals, Nikwax is water based and PFC-free.
This procedure is gonna last longer on newer garments rather than older ones, but it's still a good one to do at the start of every soggy season with most of your outer layers.
How to use NikWax on your shells, step-by-step . . .
Clean the detergent tray on your washing machine. Take it (carefully) completely out of the machine if you can, remove any excess regular laundry soap that might be in there. Put it carefully back in.
Empty out all pockets and close all zippers. Wash two garments at a time.
Start with the Nikwax cleaning solution. Give the bottle a good shake, and pour about 150 mL (for two garments) into the detergent tray.
Run the wash cycle. Nikwax suggests warm or cold water, slow spin, and extra rinse if possible.
Leave your clothes in the washing machine, and then run another cycle with the TX Direct. For this, use about 200 mL. Give that bottle a good shake as well.
If your washer has a lame spin cycle, let your clothes drip dry for a bit outside or over the tub, but don't let them get completely dry.
Put clothes in a dryer on low heat.