Ulog enables you to list past and present X11 sessions on a whole domain of machines. It is the X11 equivalent of "who" or "last" commands, with much more sophisticated options and search criteria (such as login username, hostname, display name, login/logout times, etc.). It relies on a ulogd daemon which keeps track of events (login, logout, etc.) sent via, for example, the startup and reset scripts of xdm.
glogwatch is a GKrellM plugin that alllows the monitoring of an arbitrary file, such as /var/log/messages, or a SNORT alert file, for changes. Once a change is detected, a timer is displayed showing the elapsed time since the change occurred. The timer is reset and re-armed when the user clicks on the plugin to view the file.
Chainsaw is a GUI log viewer and filter for the Log4J package. It listens for LoggingEvent objects sent using the SocketAppender and displays them in a table. The events can be filtered based on Priority, Thread name, Category name, or Message. It can also load events logged to a file.
logn (login-notifier) notifies you about logins of other users. It uses the file /var/log/wtmp for this task and scans this file for login of users. When someone logs in (e.g., using ssh, telnet or FTP) an informational line about the login is printed on your console. To ease idling around on a remote machine with firewall/NAT between you and the remote machine, logn outputs an ASCII NUL character every 8 minutes.
Trace.java is a package used by Java programmers, testers, server administrators and others to understand what happened during the execution of a program. It doesn't generate tracing statements automatically; programmers have to add them. Trace messages go into an in-core ring buffer, a disk log, or both. The disk log can be fixed size with backups. What amount of detail gets logged can be controlled at runtime or launch time. The ring buffer and disk log can be controlled separately. Different subsystems of the code can be controlled independently.