For "/post/the-title/10 /* /post.php?id=10 */"
RewriteRule ^post/[^/]+/([0-9]+)/?$ /post.php?id=$1&friendly=1 [L,QSA]
For "/posts/ /* /posts.php?what=last */"
RewriteCond %{QUERY_STRING} !^what=
RewriteRule ^posts/?$ posts.php?what=last&friendly=1 [L,QSA]
For "/posts/?what=top /* /posts.php?what=top */"
RewriteCond %{QUERY_STRING} ^what=
RewriteRule ^posts/?$ posts.php?friendly=1 [L,QSA]
For "/posts/category-name/5 /* /posts.php?what=cat&id=5 */"
RewriteRule ^posts/[^/]+/([0-9]+)/?$ /posts.php?what=cat&id=$1&friendly=1 [L,QSA]