Ask HN: How do you store/recall professional contacts

Every now and then, and more often recently, I offer to help someone out. Generally it's a little thing but the recipient is appreciative and often says in one way or another, "if I can repay the favor let me know." Or maybe I met someone with a mutual interest but there was nothing specific (or active) enough to keep in close touch at the time.

As the months go by something will come across my path where I would like to reconnect with someone, but I often can't recall the person's name, their site or exactly how we left off our last communication. I end up sifting through my email to piece the memory back together, but I get a lot of email so that task is arduous and occasionally fruitless.

So I'm asking what people use to manage their professional contacts. I know applications like Salesforce are built for this kind of relationship management, but that seems like over-kill. Could be it as simple as notes in the contact list of your email client? If someone could enlighten me on the application and methodology they use that would be very helpful.