Andrew asks about Linux-friendly eSATA controllers. A long time ago, I also looked for some - but basically no one seems to know about that, or will try to rip your eyes for it.
In January, however, I looked for (and bought) an external USB enclosure for SATA disks. As portability was more important than speed, I only asked for USB. Good, got the kit, paid for it.
The external enclosure had an external eSATA port. Not only that, it shipped with a standard PC expansion slot bracket and adaptor - Yes, it connects to your internal SATA port, and provides an external eSATA port. And, of course, it will work with your current kernel painlessly. And, of course, it is even cheaper than a SATA controller with an external port.