OpenID vs. OAuth

What is really the difference between OpenID and oAuth? They look just the same to me.

PHP Tutorial for OpenId and OAuth

Is there a good tutorial for implementing OpenId and OAuth together in PHP? All of the OpenId tutorials I've seen on the official OpenId site haven't been as helpful or as simple as they could have been. I don't think I've seen any tutorials on using both of them together. (For OpenId, I'd want to be both a provider and a consumer.) If there are no tutorials for using them together, tutorials on implementing either one in PHP would also be helpful.

Rails 3 authetication with OpenID, Twitter or Facebook

Can you suggest some working example of it? I tried Authlogic and Devise withous success.

Is Facebook an OpenID provider?

Is Facebook an OpenID provider? I know they are an OpenID supporter but do they allow people to authenticate with other sites via OpenID with their Facebook credentials?

Integrate Google, Yahoo and OpenID in android application?

I want to integrate Google, Yahoo and OpenID in my android application. I have successfully done with facebook, twitter. I had used facebook android sdk for facebook integration and twitter4j-core-android-2.2.3.jar for twitter integration. Now I am looking for Yahoo, Google and openId integration. I searched for yahoo integration also registered to get consumer key, consumer secrete key and application id. But I didn't find any jar or sdk for yahoo integration. There is for iPhone but not any thing for android.

Best OpenID Provider for iPhone / Mobile Device

Is there an OpenID provider that is really exemplary for use on an iPhone or other mobile devices?

Is Google the only OpenID provider that requires "identifier_select”?

I am developing an OpenID consumer in PHP and am using the fantastic LightOpenID library ( http://gitorious.org/lightopenid ). Basing my code off of that found in the example client script I have successfully created a consumer. However, I've run across a snag: Google requires the openid.identity and openid.claimed_id to be set to "http://specs.openid.net/auth/2.0/identifier_select" (see here ). If I do that it works but other providers (i.e. AOL) don't.

App Engine - Intermittent 500 errors on /_ah/openid_verify

I'm getting intermittent errors when logging into my app with the Google openid.