Cause why not. Soundcloud now has a nifty HTML5 embed option so the tags will use that. Rather simple:
[soundcloud]7016087[/soundcloud]
Will show up as:
The number is the song ID. This can be found in the normal embed code given to you by soundcloud when you choose the share option. An easy way to see the ID is to click share and then choose the wordpress option, you will see the ID without having to scroll through lots of HTML to find it:
Update: I just added playlist support.
You get the playlist ID in the same way as you get the ID for a track above, though the bbcode looks like this:
[soundcloud=playlist]168921[/soundcloud]