Prices are down nicely on 3G SSDs.
"G" = gigabit, 3G = 3 gigabit, 6G = 6 gigabit SATA
The OWC Mercury Electra 3G SSDs are not as fast as the 6G models, but for many if not most situations the difference is immaterial, being a huge upgrade in speed over a hard drive, particularly a laptop. The 240GB model looks to be ideal for upgrading an old laptop (cost and capacity), though MPG recommends 480GB as even better for longer term, simply for capacity reasons.
The 3G models slot into many Macs, including the 2009-2012 Mac Pro drive bays (using the Mac Pro drive sled).
Also, these SSDs are terrific cost-effective upgrades for an older laptop in particular; see Making an Old Dog of a Laptop Run Like a New One: Wow!.
Or for a MacMini (internally or otherwise), or any Mac with USB3 (via an external USB3 case), but see bus power discussion for the 960GB model below.
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The 960GB model
The 960GB model is interesting: it uses two flash modules internally as a RAID-0 stripe, and while it is a 3G SSD SATA interface, the RAID-0 striping keeps its throughput high even for incompressible data.
MPG uses the 960GB model in an OWC Mercury Elite Pro Mini USB3 case, but since the power draw is too high for USB bus power, it is mandatory to power the unit using the optional AC power adapter (wall wart). No big deal for home use: 960GB in a compact case on the desk is pretty darn awesome.
Consider also that four 960GB Electra 3G SSDs can fit into a 2009-2012 Mac Pro, for 3.84 TB of SSD storage. Totally quiet, awesomely fast.