Make Ad-hoc builds in Xcode 6 without signing in to developer account

If you are using Testflight to upload adhoc builds, it's easier. Install the Testflight app for Mac and run it. Whenever you do an archive in Xcode, it auto shows a popup whether to upload it. You need not export the build from Xcode and avoid signing in to developer account.

Alternatively, if you don't want to distribute on Testflight, you can right click (or option click) on the build in Xcode > Organizer and select "Show in Finder" and right click the archived file for "Show package contents" and get the .app. Put the .app inside a directory called Payload and zip up the the file to Payload.zip. Rename Payload.zip to myapp.ipa to distribute manually.

Edit: A long time has passed since this answer. As for now I suggest using Fastlane for building the app from command line - with proper configuration it won't require signing with dev account.

Original answer below:

I don't know how to do it in xcode, however - I've managed to do it using command line tools:

xcodebuild -configuration Release -scheme SCHEME_NAME -workspace Workspace.xcworkspace clean archive -archivePath build/Appxcodebuild -configuration Release -exportArchive -exportFormat ipa -archivePath "build/App.xcarchive" -exportPath "build/App.ipa" -exportProvisioningProfile "PROVISIONING_PROFILE_NAME"

Just select "Use local signing assets" in the accounts drop down.