If you use iCal to manage your to-do list you may want to consider Mindful. This app creates a desktop view of your events and reminders for the day similar to the daily view function of most calendars.
The best thing about Mindful is that you never need to open iCal to see what’s coming up for the day. By default the app displays events in blue and reminders in pink, but every colour used by the app is customisable (as is the opacity) so it can blend in with nearly any desktop. You can also change how many hours are displayed, the size of the app’s window and which calendars it pulls events and reminders from.
The app is $US1.99. I’m sure there are similar free apps out there, but I’m not familiar with one as customisable and easy to use as this one, so the two bucks are merited if you want to keep your to-do list in your face but unobtrusively so.