Facebook lacks a simple feature
How do you search for all of your friends that are from or in a specific location (e.g. all my friends in Namibia right now)?
Sounds like a simple enough search.
Or is this feature already implemented?
Update:
It's not linked to from the front-page - only when you do a search: http://www.facebook.com/advanced.php
Update:
And as a commenter pointed out, http://www.facebook.com/advanced.php doesn't exist anymore!
Controlling Facebook Privacy
Facebook has functionality to create friend-lists (groups of friends). Nice thing is, you can use these lists to block certain people from viewing specific parts of your profile.
Start out by creating a bunch of lists:

A few examples are (for every part you would like to control):
- No-Basic-Info
- No-Personal-Info
- No-Photos
- No-See-Friends
- No-Updates
- No-Videos
- No-Wall
If you like, you can go ahead and add people to these groups. Unfortunately, a list has to contain at least 1-person before you can use it.
Next, go to your privacy settings, then click on profile:

Customise one of the options, for example, click on the drop-down associated with Wall-posts:

Now add the list you created to hide wall-posts to the "except these people" section - in this case, "no-wall"

This is an organised way of keeping track of friend-permissions without resorting to deleting people. If you find that you would like to hide your photos from someone, you simply add the person to the friend-list "no-photos".
You could also create a limited profile for your account and by default, add all friends to it. Next, essentially work in reverse by only allowing certain lists of friends to view your profile.