I've just set up a power monitor to log voltage, frequency, power factor, etc over modbus, and I'd like to upload and graph it somewhere long-term. There are a bunch of online graphing sites, but they're mostly just Excel for the web. Some time ago I saw a site that allows posting of data via HTTP for long-term storage and viewing but I can't remember what it was, can anyone recommend anything? Data volume is low, three values every few minutes, so any kind of free account should do it, I'd just like to view trends over time and compare what it was like last month vs. this month. Eventually I'll also hook up IFTTT to alarm on the voltage going out of range, which was the motivation for doing this in the first place, but that's for another day.