Following is a short and sweet list of the best providers available that I can recommend for the following services:

Wireless Providers

Airvoice Wireless (AT&T GSM – best per-minute GSM MVNO, BYOD)
P’tel (T-Mobile GSM – best and cheapest to maintain per-minute PAYGO MVNO, BYOD)
Ting (Sprint + Verizon CDMA – great for family plan needs and heavier users, BYOD-ish)

VOIP Providers

Callcentric (Excellent VoIP providers with some of the best overall customer support, BYOD)
CircleNet (One of the cheapest local and international per minute VoIP providers, barebones features, BYOD) (Excellent VoIP provider with multiple low-latency servers, and competitive per minute billing options, BYOD)
VOIPo (Cheapest full-feature VoIP provider currently on the market)

DSL Providers

DSL Extreme (Cheap nationwide DSL provider, offers dry-loop service in Verizon regions) (Best DSL provider in California)

Rackspace Providers

Hawk Host (One of the cheapest shared CPanel based rackspace providers with good support available) (No nonsense rackspace provider for the more skilled administrator)
NearlyFreeSpeech.NET (The cheapest shared rackspace provider available for small traffic sites, geared for professionals, zero handholding)