For me, joy has been derived from the acquisition of a few types of cards and memorabilia.
1. My first vintage card (and I'm not talking about the 1983 Topps Traded Larry Bittner that came in one of those baseball card starter kits). Like many of us, my father lamented that his mother threw out all his cards. He was an avid collector of 1961-1963 Topps, especially the wood grain 1962 version. For one of my birthdays (somewhere between 10-12), we went to the nearest hobby shop, which was called Neshaminy Stamps and Coins. It had everything, literally, but it's long gone now. We went to the vintage card section together and rifled through the boxes. Two cards stuck out, a 1961 Topps Curt Simmons and a 1962 Topps Orlando Cepeda. I was able to choose one (in addition to the other gifts that day). I chose the Cepeda (for the low price of $3.00), and it was and is the first vintage card I have ever owned. Check out the grin on this guy's face.
Alas, this image is from ebay and not mine (it's in PA, I'm in CA).
2. Is that Mickey Mantle? By the time I was a teenager, I was a veteran of packs and card shows and hobby boxes. In 1996, I received a Topps Series 1 box for Hannukah (well, this was the tradition: my brother and I would go to a card store, either Baseball Connection or Toy Trains and Sports Cards and pick a box for each of us; I miss traditions). Of course, Mickey Mantle reprints were inserted in the packs. I opened the box pack by pack, and when I came upon a reprint, I literally jumped off the living room floor and showed everyone in the house. I mean, it was Mickey Mantle! in my hand. The one that was on the August 1995 issue of Beckett. The one with the 1952 Topps card that I saw sell with my own eyes for $30,000. This proceeded to happen 3 more times during the next 2 hours. I had a lot of energy then.
3. The set's complete!: This joy is all about the quest. I still feel great when it occurs. The last two sets I've completed by hand were 2007 UD Masterpieces (thanks I am Joe Collector) and 2007 Allen and Ginter base set, flag set, box topper set, etc. These had a slightly different joy since I can anticipate the cards coming through the mail. For sheer "This is the last card I need for the set and I found it in THIS BOX!" feeling, I have to go back to 1996 when I completed the 1996 Upper Deck set.
4. The autograph to end all autographs: Now I'm an adult (at least functionally), and I live far away from home (nearly 93 million miles away). My mother came out to visit during the summer for a 5 day retreat with her oldest son. We both love to go to baseball games, and she wanted to see the San Francisco stadium for the first time. So I got tickets for a game there, but then I found something extraordinary (h/t Awesomely Bad Wax for his weekly postings), Mike Schmidt, the Phillie to end all Phillies, was going to be in Sacramento at a Sacramento RiverCats game for free autographs. I asked if she minded going to another game in the same weekend. When I mentioned who was going to be there, she also seemed very excited. So, we drove the nearly two hours (with typical Bay Area traffic) to Sacramento, arrived at the stadium....and waited in the shortest line ever for a living legend. We introduced ourselves, took a picture with him, and received the large card he was signing. It was a few seconds of pure joy. The game itself was also fun (it was amateur singer night, applause for all). (I am still looking for the photo of the "event")
The joy, for me, is all about the thrill and knowledge of what you can get along with sharing the experience with those close to you. Enjoy!