While a couple of these items may be useful, some are just ummm.... curiosities. Maybe they're not quite as curious as a cat-less grin, but I have spent more than a few minutes exploring these sites. Hopefully something here will catch your attention as well.

Hacker slang from the 70’s at MIT and Stanford was the original content of this file. More recently, various terms have been added from PDP, Unix, PC and other tech cultures. It is also available in print as The New Hackers Dictionary - but the file is more up-to-date. The Jargon File
This was one of the main distributions of alternate firmware for the Linksys WRT54GL router. Depending on the options you chose, it could be a commercial hotspot, an asterisk PBX, a file server, a web server, a firewall, and of course, a really flexible router.  Although the 54GL is antiquated by now, a variety of modern hardware is supported - it's even preloaded by one manufacturer. DD-WRT
These are just plain good to have on-hand. While not exactly entertaining, they print out nicely - so you can stick them on your cubicle wall. ASCII & HTML Tables

Previously called "Asterisk: The Future of Telephony", it now has a somewhat less pretentious title.  Unfortunately, the free version is only available in HTML format (the original 2005 edition was a pdf).  Asterisk actually IS quite popular, but like most infrastructure components, you won't notice it unless it breaks.

Asterisk: The Future of Telephony
Apparently, these exceedingly solid, well insulated, and inexpensive buildings are made of just polyester/vinyl sheeting, polyurethane foam, and spray-on concrete - with a bit of rebar for good luck.  If I was living in a vacant lot instead of an existing house (and didn't have rectangular furniture) I’d definitely consider one of these structures. Home Sweet Dome
Credit card numbers are typically 16 digits long. The last four are usually printed on receipts. The first six can be looked up in the BIN database. Let's see... That leaves a grand total of SIX digits that are still secret. Of course, the last digit is a checksum for the previous 15 digits - making those “secret” 6 somewhat less so.  But since everyone is so honest, there's nothing to worry about... BIN Database
All About Credit Cards