emails via my Ipod Touch with no bother. I am assuming your settings are ok if you're able to receive them. You ask if you are missing something obvious, so pardon me for asking a very obvious question!
Did you notice the icon in the bottom right hand corner when you open your Mail app? It looks to me like a pencil on a sheet of paper - it is the "write" icon. If you tap it it will bring up the "New Message" dialogue box and the onscreen keyboard.
By the way, isn't the Ipod touch a fabulous gadget?
Hope this helps :-)