Release 1 of the Android 1.5 SDK is available for download now. Additionally, a system image for the ADP1 (Android Developer Phone from Google) is available for 1.5 now, as well.
This is the third full release of Android, corresponding to API Level 3 (Android 1.1r1 was Level 2 and Android 1.0r1 and 1.0r2 corresponded to Level 1).
This time, though, the Google map services are in an SDK add-on. A vanilla API Level 3 distribution may not contain these. Testing this is made possible through an emulator target that contains these services and one that doesn't, where even clicking on a map link from within an application won't work.
This capability opens the door to other third-party add-ons, a very exciting potential.