We use Callwave. We went from the free version to the $3.95/mo. version. This includes caller I.D. and if I am using the phone, it will let me know if I miss any calls. We also pay $1.25 to the phone company each month for call forwarding, which makes it work. The monthly fee is billed to my phone company and comes on my phone bill.
I have had it for about 2 years now and really like it.
Diane AKA Whitegloves =0)