Keeping pizza crust from getting soggy from fresh tomatoes
Here are a few things that have worked for me:


Brush oil on the dough before applying toppings.  (Already suggested)
Scoop out the seeds and guts and then dice your tomatoes instead of slicing.  This should get rid of some of the moisture.
Add cheese and then place tomatoes on top.
Stretch your dough evenly and not too thin.  


I usually don't precook tomatoes (sauce at least) because it ends up getting gummy since they get cooked twice.