If you've taken to scheduling your life via Google Calendar, take a look at the free GMinder utility. The small desktop app downloads your scheduled events so that you can quickly see what's coming up without opening a browser, or even needing to be online. You can also get snooze-able pop-up reminders, a nice touch.
GMinder is quick to set up. You provide your Google username and password and click a Download button, and it displays a list of your calendars. You can de-select any you don't want it to pull down.
From then on, you can click the app's icon in the system tray to see your upcoming events in a small pop-up window. GMinder pulls down the next 31 days' worth of events by default, and will check every 10 minutes for new events (you can change both settings if you'd like).
GMinder will by default display a pop-up alert window and play a sound 15 minutes before each event. You can hit a Snooze button to snooze an event's reminder for a set number of minutes, which is a neat feature not otherwise available for Google Calendar, but dealing with the pop-up can be a little clunky. It displays all of your upcoming events instead of just the one about which it's reminding you--and although you can click Dismiss to clear the selected event reminder, doing so doesn't make the window go away. You have to also click a Hide button.
You can bring up the same reminder pop-up window by double-clicking the tray icon, and then click a New button to add a new event (which shows up on your online calendar), or Open to bring up an event in your browser.
Gminder is a nifty little tool for Google Calendar users. The ability to quickly check upcoming events without going to your browser, and being able to snooze on your reminders, more than outweighs a somewhat clunky reminder window.