For a quick response you get what's in my head already. IOPS stands for Input Output Per Second, and is the number of individual small reads and writes per second the drive can do. This is more important for some server applications than raw throughput, because each person who visits a website may only need to have a couple of Ks looked up, but thousands of people need this little bit every second. In a spindle based drive, no matter how fast the heads move they often have to wait for the right part of the drive to spin under them. This is one of the reasons that server drives spin at 10,000 or 15,000 RPM: More IOPS. SSDs of course are beasts at IOPS since they don't have any moving parts to wait for. For a home user IOPS are most noticeable when booting up because many small files need to be read at that time.
For benchmarks, I'd have to google it. I've tried I think IOmeter before. The main drawback of many of them is that they need to overwrite everything on the hard drive to get a good reading. One other suggestion: maybe find a live linux CD with the phoronix test suite built it? I know that it has a bunch of server based hard drive tests.