Try setting last="true" to your first two rules, then adding a third rule:
<rule>
<from>/contact_us</from>
<to last="true">/contact.jsp</to>
</rule>
<rule>
<from>/about_us</from>
<to last="true">/about.jsp</to>
</rule>
<rule>
<from>.*</from>
<to>/user.jsp</to>
</rule>
This means that, if there is a match on /contact_us then the filter will stop looking for matches, and the same goes for /about_us. Anything that doesn't match either of those will be compared against the third rule, which should match anything.
In regular expressions, "." means match any single character, and "*" means match zero or more occurrences of the preceding portion of the pattern. So ".*" means match zero or more of any character.