If you're open to commercial solutions, there are several SaaS choices that are quite cheap at low log volume. For instance, Scalyr (500MB/day for $19/month), LogEntries (free up to 167MB/day), or Papertrail (33MB/day for $7/month). All will provide centralized logging and full text search, and some form of dashboards and alerting.

Scalyr provides especially powerful features for log parsing and analysis, as well as integrating system and application metrics, and it's wicked fast -- most searches run in well under 1 second. (Disclosure: I am the founder of Scalyr.)

If you're interested, the respective web sites are easy to find, or drop me a line (my email address is in my profile).