If you want to get a new daypack most any department store has them. I got two Jansport daypacks off the clearance rack at Target a few years ago. Those will last most people a lifetime, and they're guaranteed for life, so they are a good choice, but any well built one should last a long time.

I like scrounging around at "Thrift Stores" for used stuff. You never know what you'll find there, and sometimes you can find some really good stuff. I've got several wool sweaters from Thrift Stores that I use for cool weather camping, and one of my cooking pots came from one.

I've heard of others getting some very nice backpacks and sleeping bags from Thrift Stores too. I've not been so lucky as to run across those, but I haven't been very energetic in my efforts because I just don't shop much.

Craigslist, eBay, and garage sales are also good places to keep an eye on for used gear.