So, I thought we need a general thread for this. In case you've been living in a cave somewhere or possibly under a rock or even in a cave beneath a rock:What is Android
From Android's own site:Introducing Android
Which Phones Does Android Run OnThe HTC Dream, AKA The G1:
Androidâ„¢ delivers a complete set of software for mobile devices: an operating system, middleware and key mobile applications. The Android Software Development Kit (SDK) is now available.
Android was built from the ground-up to enable developers to create compelling mobile applications that take full advantage of all a handset has to offer. It was built to be truly open. For example, an application can call upon any of the phone's core functionality such as making calls, sending text messages, or using the camera, allowing developers to create richer and more cohesive experiences for users. Android is built on the open Linux Kernel. Furthermore, it utilizes a custom virtual machine that was designed to optimize memory and hardware resources in a mobile environment. Android is open source; it can be liberally extended to incorporate new cutting edge technologies as they emerge. The platform will continue to evolve as the developer community works together to build innovative mobile applications.
All applications are created equal
Android does not differentiate between the phone's core applications and third-party applications. They can all be built to have equal access to a phone's capabilities providing users with a broad spectrum of applications and services. With devices built on the Android Platform, users are able to fully tailor the phone to their interests. They can swap out the phone's homescreen, the style of the dialer, or any of the applications. They can even instruct their phones to use their favorite photo viewing application to handle the viewing of all photos.
Breaking down application boundaries
Android breaks down the barriers to building new and innovative applications. For example, a developer can combine information from the web with data on an individual's mobile phone -- such as the user's contacts, calendar, or geographic location -- to provide a more relevant user experience. With Android, a developer can build an application that enables users to view the location of their friends and be alerted when they are in the vicinity giving them a chance to connect.
Fast & easy application development
Android provides access to a wide range of useful libraries and tools that can be used to build rich applications. For example, Android enables developers to obtain the location of the device, and allows devices to communicate with one another enabling rich peer-to-peer social applications. In addition, Android includes a full set of tools that have been built from the ground up alongside the platform providing developers with high productivity and deep insight into their applications.
The HTC Sapphire AKA The HTC Magic / G2
The HTC Hero
The Samsung I7500
And it has been hacked onto a number of existing devices as shown by this wiki-stolen list:
* The Openmoko phones (Neo FreeRunner and Neo 1973) have limited support since Google's release of the Android source code on 21 October 2008. As of 4 November 2008 (2008 -11-04)[update], the whole source stack compiles, with the kernel, user interface and most applications working, but telephony, SMS, suspend/resume and wifi, which rely on lower level hardware features, are not fully working. In early 2009 Cupcake images were demonstrated and available as flashable images.
* Motorola A1200 Ming
* HTC Kaiser: a port is in progress, not all features work at the moment
* HTC Vogue
* HTC Touch Diamond: not all functions work (including Wifi)
* HTC Touch Pro
* Nokia N810
* Nokia 770
* Asus EEEPC 701
* Asus EEEPC 1000H
* Touch Book from Always Innovating
* Dell Axim x51v 
* HTC Touch HD : similar to the Touch Diamond, not all features work such as wifi and audio during voice calls
* Samsung Omnia: basic functions (no camera or wifi, occasional blockage, needs to be installed on an SD card) 
* Sharp Zaurus: Running basic version 
I guess some recommended apps should go here.