I like anveo.com, it's $2/month if you use the "free" plan and a $2/month US number. The UI is kind of dated, but the US phone number accepts incoming SMS, and they offer a drag/drop IVR type interface where you can route calls in most any way you want. Also includes in/out faxes, not that it comes up much, but when it does, it's nice to be able to do.

Note the other responses regarding some places requiring a "real" mobile number for SMS verification. Anveo's numbers won't work for this kind of thing. Similar to how Google Voice numbers don't work for it either.