Yahoo DSL is only $19.99 when you sign up with a certain SBC Long distance plan. Also, you have to figure all the charges they tack on for hooking up the phone connections; My first bill from SBC was HUGE much to my dismay.
Since you have Verizon which I heard doesnt go through the phone jack, I suggest you should consider looking into VOIP. There is a huge thread on VOIP in the Lifestyles section. You may not be able to find a cheaper DSL but you may be able to reduce your telephone bill which means in the end you'll save money...