Every time I'd google some obscure memory from childhood, or some wierd artsy or filmy thing, or a meme, I'd run into a blue or green page that looked kinda like a forum, and steered me toward more relevant links, sometimes while making me laugh.
Eventually, dawned on me to see what else this site was holding... it was like a "cool site of the day" for more days than I would ever be alive! Like memepool only with commentary and bonus questions! Hooray! Pretty soon after that, I decided I had to put my $5 in so I could post and mouth off like the rest of you. I didn't lurk too much before jumping in.
Meetups! Until then, MetaFilter was fun and full of discoveries, however it remained a somewhat abstract experience to me. But I had a hunch these people would be up my alley, so I paid attention to the meetup sidebar.
When I was a teenager in the 1980's, I had a modem, and maybe 5 or 6 other kids at my large high school had one. This reminds me of those days, calling BBS's, and eventually going to meetups to discover that there were other kids out there in nearby towns, who were somewhat like me... So!
My first meetup, I had a good time blablabla'ing with the assorted Mefites, and then we watched Brad Sucks play a show.
At my second meetup, I met someone who has the same first and middle name and was born on the same day & year as me. And, I met my sweetie there! Who knew!! (That's my absolute fondest memory -- not from MetaFilter itself, but made possible by MeFi.)
Meetups brought the human side into the site for me: the next time I peeked in on the site, the previously abstract MeFi experience had turned into into something real -- I didn't know all these people, but I knew a few of them, and felt like I lived in the same town as the rest of them. That was the first (and still the only) time that had happened to me in the internet age, via the www, that I felt like I was part of a community rather than just another transient blip on the information superhighway. And that the town is full of cool links and interesting questions and discussions and funny yuks. I like MeFiTown!! Yay!!
So that is my fondest memory: that time when I felt like I'd found a special place and that I belonged and wanted to stay here.
Also: favorites are like crack-pellets. Being sidebarred or mentioned on a podcast is like a mega-crack-pellet with super-bonus-points. Only it's good for the community. I'm pretty sure crack isn't as good for the community.