Maine to California Which way is best?

I am flying to Maine in October, and then driving back to SoCal with my brother (he is moving back).
I have never driven cross country, I would like a scenic route. We have about 8 days of travel time planned.
Any ideas?

Welcome aboard the RoadTrip America forums.

This same general route came up a little earlier, and you should also have a look at Michael's and Tim's recommendations. As they note, there are many variations on the basic set of roads that will get you there, and only you can ultimately choose the one that works best for you. But for my money, I'd head down I-95, bypass Boston on I-495, and then use I-90 and I-84 to Scranton. There, I'd take I-81 to drop down to join I-80 west as far as Akron and then use I-76 and I-71 to drop down to I-70. That would then carry me all the way through the midwest and Rockies until joining I-15 in southwestern Utah for the final drop down into southern California.

This routing does a fairly good job of avoiding the major cities of the East, but does leave you driving through or around Columbus, Indianapolis, St. Louis, Kansas City and Denver. All of those have very good through freeways but should be avoided at rush hour, of course. Whichever basic route you choose, with 8 days you actually have a little time to occasionally leave the Interstates and take some even more scenic byways. One good example would be the I-84 to I-80 connection in northeastern Pennsylvania. As Tim points out, I-81 through Scranton can get quite congested. The scenic alternative is to leave I-84 just after entering Pennsylvania and use US-209 down through the Delaware Water Gap to join I-80 at Stroudsburg. Similarly, you are going to be driving by a number of gorgeous National Parks, particularly in Colorado and Utah. Take the time to leave the main road and explore them.

Best of luck.

AZBuck

Depending on where you're starting from in Maine, you also have the option of taking some time in New England and driving through the White and Green Mountains of New Hampshire and Vermont. This will require a good portion of the first day, but the scenery is worth it in my opinion.

If you are driving a moving van (sounds like you probably will be), then I'd stick more with AZBuck's routing suggestions.