tetrahymenaRULE! Lab alum

Here is my problem, my phone is falling apart and I want a new one. I don't want to buy from the ATT store because the charge a ridiculous amount and I don't want to renew my contract. I had a friend that bought a phone from walmart which he was able to switch his phone's SIM card into and it worked. When I went to the store I can't find any phones that don't come with plans or else tracfones which have proprietary software. What where can I buy phones for a reasonable price (say less than $100) which will accept my SIM card? Thanks in advance...
Let me mention again: less than $100.
What I want is a phone that will tide me over for a few months until I get a shiny new one from signing up with a different company.

emmanuel a

Once you are already with Cingular. get the new unlocked google phone for just 149 dollars and switch you sim over. only one company has the unlocked google g1 phone and it is not t-mobile. order your phone from this company and never worry about a contract again. unlocked phone is the way to go.