These are primarily intended for benchmarking your SSDs, but they can be used to benchmark any storage subsystem such as conventional HDDs and USB drives/sticks.
AS-SSD will test your system with a massive chunk of incompressible data.
Note that you won't want to run this utility a lot on your SSD if it has a SandForce controller, as it hammers the write tables pretty good which can/will decrease the performance. You can read about it in various forums.
Then there's ATTO Disk Benchmark which will let throw a set of compressible data on your storage subsystem. This is typically more in line with what most people see in daily usage.
and a link to download (since you need to get it from a 3rd party host) such as MajorGeeks
ATTO is good for determining if you're actually getting full SATA2 or 3 speeds, and if you are running a RAID, if the system is using it properly.