I was really annoyed of seeing .svn in my greps, its even more annoying when you grepping in the absolutely unknown code, so I googled and almost right away came across this great blog entry from State Of Flux I do copy his code here but only just for the record ( without claiming any credit whatsoever)
find . -path '*/.svn' -prune \
-o -path '*/vendor' -prune \
-o -path '*/log' -o -path '*~' -prune \
-o \( -size -100000c -type f \) \
-print0 | xargs -0 grep -ne "SEARCH"