Graylog2 is an syslog implementation that stores logs in MongoDB. Messages are accepted via TCP or UDP. A Web interface allows you to view the log messages. It also implements GELF, the Graylog Extended Log Format, which is a simple JSON string that allows you to send long and structured syslog messages, which is very useful for customized application log monitoring.
Chef is a systems integration framework, built to bring the benefits of configuration management to your entire infrastructure. With Chef, you can manage your servers by writing code, not by running commands (via Cookbooks), integrate tightly with your applications, databases, LDAP directories, and more (via Libraries), and easily configure applications that require knowledge about your entire infrastructure ("What systems are running my application?" "What is the current master database server?").