Gravity Applications recently updated their Reminder widget, and I'm finding it quite useful. Now that my Dashboard isn't taking eons to load -- thanks to Snow Leopard -- it's really nice to be able to pop it up and with a few clicks set an iCal alarm for 5 minutes, an hour, a week, whatever I need a quick beep for that doesn't require a full event edit. It's simple, single-purpose and very effective.
You may know Gravity Apps from past coverage on TUAW, or for some of their innovative software projects such as Tags, Searchlight and SofaControl. These guys have been doing a great job providing software tools to meet a wide range of needs, and have proven to be eager and determined developers. The polish they push for on every application apparently shows up in their Dashboard widgets as well.