Well i am just starting to do exactly the same. For a different reason however. I am moving into triathlon and after a couple of months of practically killing myself trying to 'add-on' the other training on top of my running I realised it wasn't going to work and got myself a coach.
So - first thing - what kind of distance are you aiming for?
Then - How much time do you have? Can you take 5 days a week and do 3 runs and 2 cross training or do you 'need' to run everyday or only 3 times a week.
Decide on your core sessions. FOr me this is 1 distance, 1 speed, 1 recovery and 1 brick (run straight off the bike).
My distance is 14 because i do half marathons most of the time.
My speed work comprises long intervals (800m - 1km ) at my running club at speed determined by www.mcmillanrunning.com (and occasional hill sessions and once a month a 6km time trial - run by my running club)
Recovery and off bike running is determined by my heart rate - keeping it below 70% - feels so refreshingly easy.
My other sessions are 3 bike ( 1 long, 1 hard and 1 easy), 1 hard swim (distance one week, intervals the next) and a weights sesssion. It makes for a very full week but the running is so much less than I used to do and I can feel the difference in how fresh i feel on the recovery runs. It feels great. Prior to this change I think I did every workout either hard or medium and so never really recovered. Even though this probably looks like a nightmare week for someone not into triathlon, you could easily add in cross training of your choice into a couple of other days.