For VOIP, check out Vitelity.com which I have used with some clients and they have been happy with them.

For datacenter, I would recommend InterNAP bandwidth, available in many datacenters. Cheapest place I have found so far is Houston and Atlanta, GA, but I have not researched it recently. About $1099/month for full rack with 10Mbps of Internap bandwidth.

I have not used them but some swear by zogmo.com or steadfastnetworks.com .