I use a clip like this:



This one for the EVO I found At this online retailer for example.

And use a hook and loop (Velcro) cable tie on my stem to hold my small flip phone. It's handy and I can hear it if I get a call. Sometimes I'm out playing hooky while I'm riding and I don't like to miss an important call. Before I get called out for this I don't answer the phone if it isn't safe.