I'll add an eeprom for logging the temp now
You know there's EEPROM onboard the 168/328 chips right? That's what I used as I'm not logging historical data, just a few bytes for the min and max values.
I've just remembered, it can tick as well. I put a relay in it which flips every second. There's a switch to turn it off though, it's a bit annoying.
Oh I loove that!! I'll add a relay to my nixie version - on the hour I'm planning the flip through all the digits to avoid cathode poisoning, and if I whack the relay at the same time it'll feel like the flight boards at the airports flipping over! 
The back on my unit above is visible through perspex as well - I tried to be nice and neat with the point to point soldering. Will post a pic of that plus my schematic later (it's at home).
Cheers,