i use a mini as htpc, and have no keyboard plugged in.
I just use screen sharing if i need to do something on it.
i have friends that have a linux box for a HTPC and they use
synergy so they can use the mouse and keyboard on their laptops like the tv is a second monitor (just move off to the left of their laptop screen, and they are on the tv, and can use their keyboards there too.
I use a program called
Remote buddy. It gives you a lot more control from the apple remote, and lets you map keys to any program you want. Plus if you have 2 remotes, in the same way that you can pair a remote to a computer, you can assign different functions to each remote.
It comes with an onscreen menu that you can use to browse your files, plus you can access the same menu from an iphone or ipod touch. you can also use the menu to do all sorts of system functions like sleep, shutdown or quit or force quit a program.
it also has mouse mode, where you can move the cursor around using the direction buttons, and an onscreen keyboard also.
but the coolest function is that you can use a wii-mote with it (connects via bluetooth). it gives you more buttons (can access everything on the remote but the power button), and with a sensor bar you can point the wiimote at the screen and use it as a mouse.
for a sensor bar i have 2 IR LEDs on the top of my tv, plugged into a usb port on the mini. fairly straight forward if you have even a tiny bit of electronics experience. you can buy a battery powered one though.
