Standard library
Core:
- os, sys, string, getopt, StringIO, struct, pickle, ...
Regular expressions:
- re module; Perl-5 style patterns and matching rules
Internet:
- socket, rfc822, httplib, htmllib, ftplib, smtplib, ...
Miscellaneous:
- pdb (debugger), profile+pstats
- Tkinter (Tcl/Tk interface), audio, *dbm, ...