I've got all the fossils, but am 3, 3, and 2 away from seafood, bugs and fish, respectively. Don't even ask me about art, I've probably bought the fake Neutral Painting like three times.
I'm really close to completing my fishing encyclopedia, especially for the ocean fish! I just need the puffer fish and king salmon. I'm not as big on bug catching as I am fishing so that's a little empty, and I can't always be bothered to go diving either.
I've never been able to finish any of them. My main town has like...1 piece of art in it. I seem to keep missing Redd or not feeling up to looking for guides when he's actually there.
I've completed all of them, but I'm still working on the badges (the ones not involving completing encyclopedias). It took a very long time though, especially the diving and art. However, the members here have really helped me. I was even able to go to off season towns to complete my diving.
Since I restarted my town, I've only completed my fossil collection so far, but that's not listed as an encyclopedia I'm two creatures away from completing my diving list! Yay! 8 critters left for my insect encyclopedia, and 19 more for my river and ocean fish. I've got a decent amount left, but I'm sure I'll get it done!