Amon (named after the Egyptian Sun god or a demon) is a self-hosted toolkit that allows you to monitor web apps with a small footprint (Amon can fit in 20MB of RAM) and all the information kept in one place. It's a nice open source tool (with good docs) that can run on the smallest VPS you have. If you don't trust similar cloud solutions (some of which are not free) and you want to be in full control of your logs and performance history, then Amon is probably worth a look, especially for you DevOps folks.

http://server.dzone.com/articles/amon-lightweight-open-source