Head over to the Android Market right now and download Google Maps 5 for Android, which brings one of the largest updates this app has seen in its lifetime.
Google has taken this app to the next level with key features like Vector map graphics, 3D building models in supported cities, as well as automatic caching of the maps you use most. With automatic caching comes one of the most requested features: offline navigation. While you’ll still (right now) need an internet connection to begin your navigation, if you lose connectivity along the way you will not use your navigation like before.
Google completely rebuilt the graphical system in Maps, replacing the static tiles we’ve been used to seeing in every maps app until now with rendered vector graphics. Here’s what Google had to say about this new feature:

Previously, Google Maps downloaded the map as sets of individual 256×256 pixel “image tiles.” Each pre-rendered image tile was downloaded with its own section of map imagery, roads, labels and other features baked right in. Google Maps would download each tile as you needed it and then stitch sets together to form the map you see. It takes more than 360 billion tiles to cover the whole world at 20 zoom levels!
Now, we use vector graphics to dynamically draw the map. Maps will download “vector tiles” that describe the underlying geometry of the map. You can think of them as the blueprints needed to draw a map, instead of static map images. Because you only need to download the blueprints, the amount of data needed to draw maps from vector tiles is drastically less than when downloading pre-rendered image tiles.

Over at Google’s blog you can see an example of what the graphics look like. You may also already be familiar with an app that uses these: Google Earth. If you’re in a city that uses these vector graphics in Maps, just drag up or down your touchscreen with two fingers to change the perspective. You’ll notice that maps load much faster, and as you zoom in further you no longer have to wait for more data to download every time.
The other major feature that this new vector system allows is caching. It requires much less data to download the maps (100 times less, according to Google), so its much less taxing on your phone’s storage space and the network to save map data for offline access. Here’s what the devs had to say about that:

With this first version, Maps proactively caches map data for the places you use Maps the most—where you’re actively using it as well as places for which you search or get directions. Then when you’re plugged in and connected over WiFi, caching happens automatically. Near your frequent places, you’ll get detailed vector tiles for city-sized regions so you can see every road labeled.

Overall, this Maps update takes quite possibly the most useful Android app around and makes it much, much better. Maps 5.0 is a great way to rub your awesome Android device in the face of an iPhone owner; their maps app hasn’t really been updated in years.