Prepositions and articles should be lowercase in titles except when they're the first word or they're an integral part of a common word phrase. (Naturally none come to mind right now but in the latter case you can usually tell because it seems weird not to capitalize it because you'd never say the words separately.) I also think they should be capitalized when they're the last word of the title.
One place I always capitalize articles is in band names of the form "Joe Dude and The Other Guys." Using "Joe Dude and the Other Guys" seems wrong to me.