For the UOG website google touringplans. However it is only for WDW not DL. DL doesn't have a crowd calendar because it isn't really needed. If DL is too crowded you just pop over to DCA. The parks are right next to each other and it only takes 5-10 mins to parkhop.
I would add that the lack of a crowd calendar at DLR is not because DLR is not as crowded. It is because there is less of a demand for planning resources.
Most people going to WDW are on a longer vacation from out of the area. DLR as a resort draws less than half the visitors as WDW and on top of that a much higher percentage of visitors are SoCal locals on day trips. Hence the demand for planning resources in general is much, much lower.
Does that mean you do not need to plan for DLR? Well, I do think it is true that DLR requires less planning. But some level of planning is worthwhile IMO.
As far as dealing with crowds, what MrsJackSparrow4Life said above is good advice. The distance from the DL gate to the DCA gate is less than 100 yards so parkhopping is easy.
If you want to gage crowd levels that Disney is expecting you can do that by looking at the park hours. Longer park hours means more expected crowds.
o 8AM-Midnight hours at DL means maximum expected crowds (equal to 8-10 on the touringplans website)
o 8AM-11PM means crowded (equal to 7-8)
o 9AM-10PM or 11PM (moderate crowds 6-7)
o 10AM-9PM (light crowds 5-6)
o 10AM-8PM (least crowded 3-5)