There are a number of resources online dedicated to the T206 white border baseball card set. Here’s a few sites I recommend. I’ll update this page more as I find new resources I trust.
The best T206 related site in my opinion.
This site is nicely done and features a nice overview of the set, checklists and more. I tend to use this site most often as a general price guide.
This site is dedicated to the book, The T206 Collection – The Players and Their Stories, by Tom and Ellen Zappala. I highly recommend this book as it provides a wealth of knowledge about the actual players, include statistics and interesting facts.