I've been working in the Asterisk industry for a while now. The SIP providers I like the most (in the USA) are:
1. Flowroute (http://flowroute.com
) - Cheap DID, rates, varying plans (for personal and business usage), reliability, unlimited channels, nice website, free trial (doesn't require a credit card), asterisk setup instructions that actually work, awesome customer service, easy to pay (you add credits to your account via amazon pay), and again--awesome website.
2. voipsms (http://voip.ms/
) - Cheap DIDs, rates, caller ID name (optional), powerful website with tons of features / options, great support, cheap international rates to Canada.
Everything else is second best compared to these two. By far, the best SIP provider I've ever worked with is flowroute, and a close second is voipms. In my own personal and business usage I use flowroute primarily and voipms as a backup. I couldn't be happier.