Facebook Home, the social network's newest product that basically reworks your Android phone into a Facebook-centered update and messaging device, is only available on five phones right now. Being an Android app, however, there is already a way to load Facebook Home onto nearly any modern-ish Android device.
If you don't have a Samsung Galaxy S3 or S4, an HTC One or One X, or have a pre-order in for the HTC First, you're not shut out of the Facebook-as-starting-point Home app. Assuming your phone is running Android 4.0 or later, and it's not entirely locked down to prevent installation of unofficial apps, you've got options.
The xda-developers forum, the true headquarters of unofficial Android happenings, has a post with unofficial Facebook Home app downloads and simple instructions. The short version for those familiar with "side-loading" apps is: grab those APK files, uninstall Facebook if it's already on your phone, install those APK files (and Facebook Messenger, if you'd like the full "Chatheads" experience, and be sure to select "Facebook Home" the next time you tap the Home button on your phone.
The more detailed version:
Uninstall Facebook from your phone (if you can). Open all your apps from the center "drawer" on your phone (or tap the little arrow, on some phones, that contains you full app list). Press and hold on Facebook, then drag it to the top of your screen, until "Uninstall" or a trash can icon shows up.
Ensure that "Unknown sources" is enabled on your phone, to allow installation of unofficial apps. Head to the Settings app/section of your phone, then into Security, and check the box for "Unknown sources." If there is no such option, your phone may have that option disabled by a group administrator, or possibly your carrier.
Download the unofficial, unlocked Facebook Home apps from xda-developers. Each of the links on that forum post leads to another site, where you'll look for a dark gray/black "Download" button.
If you downloaded those apps directly from your phone, you should grab Astro File Manager and install it on your phone. Then you can head into Downloads from your main app list, select the .rar files you downloaded, then--finally, then--tap each app package to install it. You'll be prompted to approve the permissions requested by Facebook and Home, and they are extensive. But if you're in for this kind of Facebook total awareness, you can tap "Allow" and proceed.
Load up Facebook and enter your Facebook credentials to log in. Then load up the app named "Home," and do as it suggests: set Facebook Home as the "Always" handler for every time you tap the Home button. Install and authorize Facebook Messenger, too, if you would like the Chatheads-style integration.
Play with Facebook Home, check out how it changes your Facebook experience, and enjoy Mark Zuckerberg's version of a "people-centered phone." If you get tired of it, or just want to switch to your standard launcher, you have two options: uninstall Facebook Home, or clear it out as the default handler for your Android home screen. To do that, head to Settings, then into Apps, scroll down to the Home app, tap it, and then tap the "Clear deafaults" button inside its settings.
I successfully installed Facebook Home on my Galaxy Nexus (Verizon version), and have seen others reporting successful installs on other phones and tablets. But your mileage may certainly vary. And, from my viewpoint, you're not quite missing out on the best thing happening if you can't get into Facebook Home just yet.