1. To integrate things and ical, look here. This will put all your things next and today items into ical.
2. To integrate mail with things, use this script. Place it in your mail scripts folder (User/Library/Scripts/Applications/Mail), or put it anywhere and use the free beta version of Mail Act on from here or you can download the latest full verion from here). It will take the current email and turn it into a things todo without you even leaving mail.