Oops, sorry did not see the [R] at the end
My previous post is not 100% accurate...
I see you're trying to redirect the URLs without the trailing slash to a correct URL.
RewriteRule ^(category|joke)/([0-9]+)$ http://www.domain-name.com/$1/$2/ [R=301]
RewriteRule ^category/([0-9][0-9])/$ http://www.domain-name.com/index.php?sbcat_id=$1
RewriteRule ^joke/([0-9][0-9][0-9])/$ http://www.domain-name.com/index.php?sbjoke_id=$1
This would be the correctly optimized form... Note the [R=301] part, which forces the 301 response for your redirect...
I assumed you want to redirect the /category/999 URLs to /category/999/ don't you? With your code you were redirecting it to /index.php?sbcat_id=999