I'm new to the site. In fact I just registered, just to say this:
While I'm glad that the basic idea of how to take images from remote sources and include them in a Gallery control, this is a HORRIBLE HORRIBLE tutorial.
NEVER EVER EVER EVER for the life of you put network related code in your UI thread! EVER. If you use this code as is, you'll never end up with an app that will work smoothly. I might be new to Android development, but even I know this is a HUGE no-no. If you're wondering why things are slow with this, re-think on how to get this working. Put it in a separate thread or even a service (that you close after it's complete) if need be.
But just never put your network code in the UI thread.