The mouse is a Logitech MX-700 that I've had for eons. I used it with my Powermac G5 when I first bought it, and I still use it with the mac mini. I really need to replace it at some point. The paint is wearing off the buttons.
The keyboard is just a standard Apple keyboard with 10-key keypad that I bought with the mini. I needed to sell my Powermac, and the keyboard had to go with it, so I decided a brand new Apple keyboard was in my future. I didn't think I'd like it, but so far, it's been great!
The ACDs were from my powermac as well. They're beginning to show their age, but they still look great! The newer ones are a lot brighter, but for home these work just fine. They're right around 7 years old now. I've gotten my mileage from them for sure.
I would eventually like to get a new 24" ACD to replace the dual 20's. Even though I'd be going to one monitor, the clarity and quality of the new display is excellent. Plus, I'm using the old external isight. It'd be nice to have one built in.
Enjoy your new mini!
I really hope Apple releases a 21.5in ACD for around $400-$600. I'll buy it immediately.