I read somewhere that one, or both of these applications can sync to your computer with Scrivener. I wanted to know which one before purchasing on my ipod touch. Can you be of assistance?
Not TextExpander, I think — probably TaskPaper. I suggest running a search for those terms on these boards.
Both TaskPaper and WriteRoom can one-way synch directly with Scrivener through the SimpleText.ws web service (which also provides a browser-based way to access your files from anywhere). You can set this up in the File/Import menu. Do note, however, this isn’t really “synching”. It’s just copying files from the SimpleText.ws server into your project. Because Scrivener is a rich text editor and these programs are not, it doesn’t support uploading to the server because that would destroy your formatting. For some that might not be an issue, but for others it will, and so the “path of least support woes” has been taken. 
TextExpander, as noted, is another tool that can be installed on your iPad or iPhone which makes it easier to type, and it is compatible with at least WriteRoom—but probably TaskPaper as well.