I have been using Newrelic for some time now, let me say the support and features are decent. However there are a few shortcomings that would cause people who are just starting out or playing in a lab (as is my case). To disregard the service:
-The fact there is only 60min retention on a free account
-The fact I cannot embed my graphs into my own web front-end on my free account.
I know the term nothing is for free, but considering even the paid embedded graphs contain a giant new relic logo, and even if I were able to embed my graph on a free account I would only have 60min anyways so why not let me? I mean hey if I embed it and they keep their logo on it why not let me do it on my free account. So I got thinking. There has to be something better out there that is perfect for my home lab. And there is!
I present GraphDat (updated they were purchased by a company called Boundary), this application is 100% free. The nice thing about GraphDat is not only is it free but I can see up to 3 hours retention on my graphs free of charge, have unlimited servers, and I can embed it into my own front end so I can keep an eye 24/7 on whats going on. Not only that but the customization features of GraphDat are way better for building your graphs. They do lack monitoring individual disks something NewRelic does do well. But they are looking alot better day by day.
Updated 2013-5-10
Here is an example image of a month retention on GraphDat.
And a example of how the product can be used to create custom embedded graphs.