os.mkdir raises a generic exception if an error occurs, but typically you need to ignore preexisting directory errors. Here's how to ignore them:

import os, errno, sys

myPath = "/path/to/dir"
try:
    os.mkdir(myPath)
except Exception, e:
    code, st = e
    if code != errno.EEXIST:
        st = "Error creating directory '%s': %s" % (myPath, str(e))
        sys.exit(1)

To zip up the contents of a directory (selectively), use find and zip:

$ find . -type f -name "*.jpg" | zip -@ myimages.zip

You can use RSS feeds to create live bookmark menus in Firefox. Using the menus, go to Bookmarks -> Manage Bookmarks -> File -> New Live Bookmark. Enter RSS feed information. In your bookmarks menu you'll have a directory-like listing of the RSS information.

If you use pushd and popd to maintain your directory stack, then ~N (where ~0 is the top of the stack) will expand to the appropriate directory in the stack. For example:

cygnus:~$ pushd usr
~/usr ~
cygnus:~/usr$ pushd /etc
/etc ~/usr ~
cygnus:/etc$ pushd /usr/lib
/usr/lib /etc ~/usr ~
cygnus:/usr/lib$ cd ~2
cygnus:~/usr$

Furthermore, you can make cd use pushd and popd functionality implicitly:

~> DIRSTACKSIZE=8
~> setopt autopushd pushdminus pushdsilent pushdtohome
~> alias dh='dirs -v'
~> cd /tmp
/tmp> cd /usr
/usr> cd bin
/usr/bin> cd ../pub
/usr/pub> dh
0       /usr/pub
1       /usr/bin
2       /usr
3       /tmp
4       ~
/usr/pub> cd -3
/tmp> dh
0       /tmp
1       /usr/pub
2       /usr/bin
3       /usr
4       ~
/tmp> ls =2/df
/usr/bin/df
/tmp> cd -4
~>

(Note: The text above is taken essentially verbatim from http://www.b2pi.com/zsh/Intro/intro_6.html.)

Download an entire directory tree:

$ wget -r ftp://username:password@site/path/to/suck

Make sure you always specify a path free of symlinks. This can be pretty tough, though. An alternative approach is to use namei to track down symlinks:

# namei /usr/X11/bin/xterm
f: /usr/X11/bin/xterm
d /
d usr
l X11 -> X11R6
  d X11R6
d bin
- xterm

If you have a bunch of files in your home directory and you want to push them into ~/sort, create the directory and then do the following:

$ find . -type f -maxdepth 1 ! -name ".?*" | xargs -I '{}' mv '{}' sort

Note: GNU xargs uses -i. BSD versions use -I.