Google Maps has had a great interface that makes it really easy to use public transportation (bus and light rail) for almost a year now (if not longer). Check if your cities public transportation service is part of Google Transit at this coverage page: Google Transit Coverage.
Denver's public transit system, the Regional Transportation District (RTD-Denver) became a part of the service a few months ago and I have been using this service ever since. It is easy to use and much better than the interface provided at the RTD web page. Here is a screen shot of it in use:
The web page allows you to specify a time in the future and also shows 3 upcoming departures, allowing you to select the one that would work best for you. In addition Google Maps will also use multiple services to determine the best method for you to get where you are going.
That's all fine and dandy. But what do you do when you are out of your home and no where near a computer.
Just this last week I found that Google Maps Mobile supports public transit mapping. So here is a series of images taken from my BlackBerry that shows how to get RTD bus/light rail information while you are on the go. (This should work on any cell phone with a browser on it too, only the steps might be different. I am using a BlackBerry Pearl for this demo).
My BlackBerry home page
Selecting the Google Maps application icon
Home page of the Google Maps application for BlackBerries.
Setting up for directions. (Insert a start and destination address - which can be via address or by pointing on the map).
Clicking on Show directions - will show you the familiar directions list for taking your car to the destination. But hey you like to be green. So you try out the Transit tab.
The transit page adds a third option to the standard Start and End points - which allows you to specify the time at which you wish to depart. (You can instead also choose the time at which you wish to arrive at your destination, more on that later).
Clicking Show trips will, just like the desktop version, show you the next 3 trips from your start location.
Choosing one of the 3 trips will show you the itinerary for using public transit. (As can be seen from the above screen shots, the route shows you where the bus stop is, as well as factors in walking time to the bus stop into the itinerary.)
The interface also allows you to quickly find trips starting earlier or later.
Finally, if you want to determine a trip that is to start on a different date, then you click on the Date & Time button and set up the time at which you wish Google Maps should search for trips. (by default Google Maps searches for trips that are set to start from the current time). Finally you can decide if you wish to get trips that begin from your start point at a given time or if they should be scheduled such that they arrive at the destination at a certain time. (Extremely useful when you are trying to get to work at a certain time and don't want to leave a minute too early.)
More information is available in this post from Google Blogs, as well as a video that demos it use.
This is one feature that just aint there in Microsoft's Live Maps.