These are from the Apache Mod Rewrite Guide. These are killer scripts in my estimation. Enjoy!!

- Time-Dependend Rewriting

Description:
When tricks like time-dependend content should happen, a lot of webmasters still use CGI scripts which do for instance redirects to specialized pages. How can it be done via mod_rewrite?
Solution:
There are a lot of variables named TIME_xxx for rewrite conditions. In conjunction with the special lexicographic comparison patterns <STRING, >STRING and =STRING we can do time-dependend redirects:

RewriteEngine on
RewriteCond %{TIME_HOUR}%{TIME_MIN} >0700
RewriteCond %{TIME_HOUR}%{TIME_MIN} <1900
RewriteRule ^foo.html$ foo.day.html
RewriteRule ^foo.html$ foo.night.html

- Host Deny Using External File

Description:
How can we forbid a list of externally configured hosts from using our server?
Solution:
RewriteEngine on
RewriteMap hosts-deny txt:/path/to/hosts.deny
RewriteCond ${hosts-deny:%{REMOTE_HOST}|NOT-FOUND} !=NOT-FOUND [OR]
RewriteCond ${hosts-deny:%{REMOTE_ADDR}|NOT-FOUND} !=NOT-FOUND
RewriteRule ^/.* - [F]