NewerTechnology is one of the companies that seems to have an adapter to make just about anything fit into the USB port. The latest adapter from the company is one that will let you take your eSATA external HDD and adapt it to fit into a USB 3.0 or USB 2.0 port. The USB 3.0 use will make the data transfers much faster than eSATA is capable of. The adapter is called the eSATA to USB 3.0 Adapter.
This thing will be great if you have an external HDD that you use for backing up lots of data that has only eSATA connectivity. You can hook the HDD and adapter to your USB 3.0 port and get much faster transfer of data. You can also use the adapter to plug that eSATA only external HDD into a USB 2.0 drive in a pinch.
The adapter doesn't provide power for your eSATA HDD so you will need to plug it into the wall outlet. The adapter kit does ship with the USB 3.0 cable you need, but you will have to provide your own eSATA cable. You should have the cable for eSATA and power already. The adapter is shipping right now for $29.95.