What are ways to distribute Android app during Beta testing?

Unless you distribute it through the Market, you'll have to require users allow "unknown sources." I don't think this is such a bad thing; it will help underline to beta testers that it's not a finished product. And likely most who would be apt to participate in a beta test would be savvy enough to change the setting. Or, go ahead and distribute it through the Market, but well labeled as Beta. Lots of developers do so: http://www.appbrain.com/search?q=beta If you go that route, you may want to build in a mechanism so that the beta expires once the finished version is released. (And just to add some anecdotal information, most Android betas I've participated in have distributed the app as an email attachment or with a URL to download it from.)

I'd like to add an option to great answers provided to your question. If you need to beta-test your app and distribute it quickly and securely, you'd probably like to have a private app store. I guess you'd also probably like to get the user to access to a specific app and then revoke the access to the app (user or device).The easiest then would probably be to look for a private app store provider.You can use a http://www.appaloosa-store.com/?utm_source=quora&utm_medium=content&utm_campaign=social. Through a MAM, IT teams/dev are able to deploy and control access to mobile apps developed internally. They can either install this private store on company-provided or "bring your own" (BYOD) devices such as smartphones and tablets.Usually you only need the user's email address to give or revote him/her access to your app. Then it makes your distribution easy and there is no more problem with a potential "unknown source" with your Android App.Below is the process implemented with a private app store: My company http://www.appaloosa-store.com/?utm_source=quora&utm_medium=content&utm_campaign=social offers such service which could be of your interest, drop us a message if you'd like more details, we'd be happy to help!

Effective beta apk distribution, getting crashes as well as feedback from early adopter is known problem in android community. But Zubhium , platform for android devs solve this problem as it offers over air beta distrbution. As a dev 1. Just upload apk and email address of users whom you want to distribute beta , and click send. That's it . :) Platform will invite users and keep a track of who, when and where downloaded,  Also it will followup with users who downloaded beta for feedback.  You can view , reply , communicate back with users from platform. Optionally you can integrate crash reporting services to get crashes during beta. It will provide granular details like network, device info with exception details. It also does lot more stuff. Check out http://www.zubhium.com

I will be experimenting with this beta testing product: http://hockeykit.net/ I've used https://testflightapp.com/ and found it really useful for iOS testing. Pretty simple using iPhone user's UDID

We at http://www.betaglide.com would love to work with you for beta testing. BetaGlide not only allows you to distribute your app aming beta users but also measures information such as CPU  Usage, Memory Usage, Events, Session Recording, User touch data, Logs  and events as a beta user uses the application.

If you don't want something as public as market (although with so many apps now it's easy enough to hide in the crowd) then you can simple host the apks on your own server and send the beta users an email with the URL (text and/or QR Code). The user then just scans the barcode with their device and can easily install your apk.

You may also want to give this new product out, called AppLyzer. which during beta testing sends logs to server for analysis. it is currently paired up with Splunk. http://www.myapptest.com. you can get a free copy now. and view demo.

The Beta Family will help you find great Android testers and distribute your apps to them. http://www.thebetafamily.com

You can also submit your app on http://Soc.io Mall for fast distribution: http://mall.soc.io/