I remember:
Playing Quake 1 on dialup and feeling like a legitimate hacker when you managed to connect to a working server
Geocities websites with lime green text, Times New Roman, on a black background completely filled with rotating skull .gifs
Hamsterdance.com
Getting a 2-hour AOL trial CD and actually thinking "oh, wow! Two whole hours free Internet!" instead of tossing it in the bin
Downloading Sega ROMs from emux.com and waiting about half an hour for a 2mb file to download
The tinny, toilet-flush sound the old dialup modems used to make
Having to unplug the house phone if I wanted to "surf the web"
Napster, Gamespy, Limewire...
"OMG, I have a download rate of 4kb/sec! My modem is ON FIRE today!"
Images loading one-by-one on websites
The first time I visited goatse.cx by mistake (tip: don't)
The first time I visited tubgirl.com by mistake (ditto)
ICQ and MSN Messenger
Using Yahoo chat forums and every last bastard and their dog having a screen name derived form The Matrix or declaring their love of Eminem
Late '90s internet porn sites - no popups, but then again you were lucky to get a postage-stamp sized Quicktime video playing reliably without cutting out a few seconds in (in a new window, naturally - videos playing in a browser? What sorcery is this!?)
Trust me guys, the internet was TERRIBLE right up until the early to mid 2000s. You missed precisely nothing if you weren't there in the beginning.
More recently:
Weebls' Stuff when it was actually good
VG cats back when it used to get updated
Youtube Poop music videos back when it was a new and funny concept
Sigh... :/