The iMac (intel models, since the first ones) and all of the MacBook Pro and MacBook models use the same exact RAM modules, which are PC-5300 DDR 667Mhz. The chip is a small, about 2.5" chip, they come in capacities ranging from 512k to 1GB to 2GB. Chip looks like this:
OK, I just checked with Apple Tech specs, and it appears you may be right about the CURRENT model Mac Mini - says it uses PC2 5300 667MHz.
The previous versions used a 4200 model RAM chip which was a different form factor, and RAM installation on the mini has always been a bitch (people using putty knifes and sometimes cracking their mini to get it opened). The way I see it, it would just be easier to get your mini equipped with 2GB straight from Apple, or buy one on eBay.
Anyways, since that seems to be the case -- The Mac Pro and the xServe are the only ones to use different RAM, they use FB-DIMMs which are buffered and have a heatsink built on. All the consumer Mac lineup appears to be using the PC-5300 DDR2 667MHz chips.