The best value in (just) streaming is by far Shoutcast. Many data centers offer Shoutcast hosting/serving. You push your audio to them and they redistribute it. This means two important things. First, since you are pushing your audio at the data center's static IP address, you don't need a static IP yourself. This is frequently a $50 dollar per month price (or more) difference-most DSL or cable that comes with static IP is considered business class, while dynamic IP DSL or cable is priced as consumer. Second, since the data center is buying bandwidth wholesale in bulk (as opposed to you paying retail for it with cable or DSL), they can retail it to frequently for less than you can pay for it yourself. As an example, here's the Shoutcast provider I use for my Barix stream, b2netsolutions:
http://www.b2netsolutions.com/shoutcast-servers-hosting.htm
As you can see, you can buy a 25 listener 128 kbps package for $33.75 a month. The cheapest static DSL I can find is here:
http://www.dslextreme.com/Services/Internet/DSL/Details.aspx Look at the Express pricing.
It's priced at $44.95 a month for 1500/384 service. This gives you exactly three 128 kpbs streams-and completely maxes out your upload. Another 5 bucks a month gives you another 3 streams (for a total of six). Why would you possibly want to do this when you can buy 1500/384 dynamic service AND a 25 listener Shoutcast package for $53.70 a month?
Actually, it's even less because he's giving a 15% discount right now, so the price is actually $48.65 a month. Another bonus is that since you're only using 1/3 of your upload (only pushing one stream to Shoutcast), you still have the use of the DSL for other things.
His prices are about average-if you Google shoutcast providers you'll find hundreds of suppliers priced similarly. The only thing you DON'T get is music licensing-you have to pay for that by yourself.
The encoder can be free if you use Winamp and the Shoutcast DSP plugin. The plugin does MP3 and AAC+.
Barix Instreamers also do Shoutcast encoding (MP3 and MPEG-2).