I recently purchased a Motorola Droid Phone and had problems connecting and staying connected to my home network via the WiFi.
I have since resolved the problems and the phone works perfectly on my home network and public sites.
I found a great tool to assist those with similar problems. On your Droid is the Market place Apps Store. I downloaded the Free application Wifi Analyzer.
I then used the phone to examine the networks in the area including my own and the signal strengths.
I had an IP conflict with my Range Extender and utilized the Wifi analyzer to make sure the network and Range extender were working properly. I now have great service in my home which I can visually examine on my droid.
I hope this is useful to others with WiFi problems.