To use the maximum memory isn't easy because you need to put in an older 1066MHz (aka DDR3-8500) part to get the cheaper 1333 Mhz (DDR3-12800) part to run, but just realized the way to do this is to get five DDR3-10800 and five DDR3-12500 and put one in each as the MacBooks will go to a lower speed on the lower part.
Here is what we have:

• Mac Mini Mid 2010. Right now at 10GB has a 2GB DDR3-8500 and 8GB DDR3-12800 and we've got a spare 8GB DDR3-12800 stick and need a 8GB DDR3-8500 to get this to 16GB, but no one seems to make an 8GB DDR3-8500 stick, so best thing to do is to get a 4GB stick at 8500 and this gets you to 12GB. 8GB DDR3-8500. It is actually quite hard to get this memory at this slow speed. Newegg doesn't have any and Amazon either. Only OWC has this part at $85 a piece compared with the typical$65 for memory like this, so is it really worth it to get from 10GB to 16GB. Probably not. So we pass on this although eBay has it for $70 so maybe worth it to try that. • iMac early 2008. This has the current maximum of 6GB (2GB plus 4GB) installed • iMac late 2009. Has 4GB stock (iMac 11,1). It officially supports 16GB, but you can actually upgrade it to 32GB with te latest EFI and 64-bit OS X. It also appears and recognize at least 1333MHz (DDR3-10600 vs DDR3-8500 1067MHz) memory. And some report they could get 2x4G of 1600MHz DDR3-12800 working. The thing has four memory slots, so you need 4x8GB and since DDR3-8500 is hard to find, get DDR3-10600 or DDR3-12800. This is useful for those big graphics applications like DxO where I'm just out of memory. As another aside, you can replace your optical drive with an SSD as digging out your actual hard disk isn't easy with the main that you need is a set of suction cups to take the front glass out so not the faint of heart and removing the panel as well. • 2 x MacBook Pro. 2x4GB DDR3-8500 and according to Everymac, this is the maximum and it is what we have from our last upgrade. And one of these needs a new SSD • 3 x MacBook. 2x2GB DDR-8500 in them now, where we want to get is to 6x4GB DDR3-8500 or 3x4GB DDR3-8500 and 3x4GB DDR3-12800. Net, net, here is what we need in summary: • 4x8GB DDR3-8500 or above for the iMac. The stuff isn't cheap, 2x8GB of PC3-12800 is$127 at Amazon so a full 32GB upgrade is $250 plus dollars, so the better answer might be to add 16GB (and we have a spare 8GB stick around already). • 3x4GB DDR3-8500 for the MacBooks • 3x4GB of either DDR3-8500 or DDR3-10600 or DDR3-12800 depending on cost • 256GB SSD for the MacBook Pro. SSD Review recommends the SanDisk Extreme 240GB at$175. Tom's Hardware recommends the SanDisk Ultra Plus which uses nCache to operate in SLC mode while the Mushkin Enhanced Chronos Deluxe at $175 from Newegg is good and cheap. Another option is the Kingston Hyper X 3K or if you really don't want to worry about it 500GB Samsung 840 at$340 is actually a lower cost per bit or if you really don't want to think any more you can get a terabyte SSD now! (well almost the Crucial m500 is $600 for 950GB). See XBitLabs for a performance decoder ring based on the type of flash used So what is the lowest cost way to get true DDR3-8500 memory, here are the newegg and Amazon choices: • Newegg 4GB DDR3-8500.The best rated is the$34 G.Skill FA-8500CL7S-4GBSQ. So this is the memory to buy for the lower speed. So best option is to find some older 2GB memory that was recycled and then you end up with 6GB machines, still way better than 2GB!
• Newegg 4GB DDR3-12800.The lowest cost best rated is the G.Skill F3-12800CL11S-4GBSQ for $33 and the G.Skill is$63 so just about like Amazon but DDR3-10600 which is just fine for us G.Skill F3-10600CL9D-8GBSQ for $63 from Newegg. Frustratingly the single pack is$33, so you have to pay a little more.
• Newegg 8GB DDR3.

Amazon Computer Memory DDR3. Amazon is much harder to figure out because their search isn't as good:

The net is that getting the same sticks seems like a good idea and about the same price although the Crucial PC12800 looks like a bargain at \$31 for 4GBx2