I use the free DS Clock from Keep your time synchronized with Atomic Time servers, using customizable digital desktop clock. You can use various fonts and standard formatting like "MMM dd yy hh:mm:ss tt" etc. You can display multiple time zones. You can synchronize your PC clock with it with a couple dozen internet time servers, or add your own synchronization time server. I put it in the right top corner of my monitor customized to occupy the exact minimal space I want and still be visible.

I suggest to visit: Bluefive software - freeware system and desktop utilities for a good Alarm clock

Theres a cool one I use called T-Clock 2010.

I like it because it stays in the task bar and you can have it show seconds.

There are also bunch of other features including the ability to have multiple alarms and an hour chime.

Enjoy!