Using WMF 5.0 or WMF 3.0/4.0 with the PackageManagement and PowerShellGet modules, you can search for and install PowerShell modules from the PowerShell Gallery using the Find-Module and Install-Module cmdlets.
Therefore, I will not be updating this post anymore.
This (frequently updated) post contains links to useful PowerShell Modules. If you have a suggestion for a module to be added to the list, please add a comment at the bottom of this post.
Allows a much easier management of permissions on files and folders using PowerShell
Provides an easy way to view and modify security descriptors for most securable objects in Windows, including files, folders, registry keys, services, printers, shares, processes, and more. Pretty much any action possible from the ACL Editor can be performed with this module.
Active Directory Replication:
Managing Active Directory Sites, Site Links and Subnets very easily with PowerShell. Also checking the Active Directory Replication is easy and richer than repadmin.exe, the cmdlets in this module do return objects and not just text. So no more boring test parsing.
The module gives access to the Kerberos ticket cache. It can read and purge tickets of the current logon session.
Public Key Infrastructure:
This module is intended to simplify certain PKI management tasks by using automation with Windows PowerShell.
PowerShell Community Extensions:
PowerShell Community Extensions (PSCX) is aimed at providing a widely useful set of additional cmdlets, providers, aliases, filters, functions and scripts for Windows PowerShell that members of the community have expressed interest in.
Manage Windows Update on a computer system running Windows. Whole module contains set of functions to check, download and install updates from PowerShell.
Exposes Windows Installer functionality to PowerShell, providing means to query installed product and patch information and to query views on packages.
ShowUI is a PowerShell module to help build WPF user interfaces in script. ShowUI makes the complicated world of WPF easy to use in PowerShell. You can use ShowUI to write simple WPF gadgets, quick front ends for your scripts, components, and full applications.
Windows Azure PowerShell is a module that provides cmdlets to manage Windows Azure through Windows PowerShell. You can use the cmdlets to create, test, deploy, and manage solutions and services delivered through the Windows Azure platform.
Get, Set, Remove and Test registry keys and values
The PSTerminalServices module contains functions to manage Terminal Services (including RemoteDesktop) sessions and processes.
Active Directory SID History:
The functions provided in this module will give you visibility into the status of your SID history throughout the Active Directory Forest, help you translate SID history in NTFS ACLs, and easily target SID history removal.
Local User Management:
This Windows PowerShell module contains the following functions: New-LocalGroup New-LocalUser Remove-LocalGroup Remove-LocalUser Set-LocalGroup Set-LocalUser Set-LocalUserPassword Test-IsAdministrator
Edit, convert, add filters, get and set EXIF properties and other manipulations to image files
The PSFTP module allow you to connect and manage the contents of ftp account. Module contain set of function to get list of items, download and send files on ftp location.