Both Timer Widget and Countdown Widget now have ringtone notification support. This can be configured in the settings screen. To enable mp3 support simply install the free "Rings Extended" app provided by Google on the Android Market.
Both Timer Widget and Countdown Widget also now have full font color configuration. Use the RGB sliders or enter hex values to pick from 16 million possible colors.
Also, I now have all three of my timing widgets in a single bundled version on the Android Market. Search for "Timing Widgets" to get all three in one download at a discounted price. This pack includes the latest version of Countdown Widget, Timer Widget and Stopwatch Widget.