I'm not sure what list you're talking about - but I put up a list a few months ago, and it has basic sort capabilities.
http://halo.bungie.org/showchallenges.php
You can sort by any of the following fields:
challenge_id, type, image, title, description, value, date
(some are more useful than others
)
Just add ?o=sort_type to the end of the URL (replacing sort_type with one of the above list, of course).
You can look for specific challenges, if you know their names (or parts of their names) - just add ?c=title_fragment to the URL.
(Example:
http://halo.bungie.org/showchallenges.php?c=kettle will show you all the Drop Pod challenges.)
And you can search for specific challenge types (as indicated by the images that appear with each one) with an addition of ?i=img_num - so, for example, you could look for all campaign challenges with
http://halo.bungie.org/showchallenges.php?i=2
The types are:
0: multiplayer
1: weekly (there's a single screwup on Bungie's part with this)
2: campaign
3: firefight
4: miscellaneous (or complicated multiplayer)
You can also combine parameters:
http://halo.bungie.org/showchallenges.php?i=2&o=value will show you all the campaign challenges, sorted by value.
I never built a real interface for using it - but if you know the parameters, you can do most of your searching/sorting here.