Windows Vista

Power Management
Tweaking Windows Vista so it can run a bit faster - also the standard theme requires the "Desktop Window Manager Session Service" which can be disabled and will save about 20MB memory.
C:\Windows\winsxs - this is the folder for "Windows Side by Side" - which keeps multiple copies of DLL's (including different versions of the same DLL in many cases) in order to let multiple applications run without any compatibility problem. This feature was first introduced in Windows ME as the solution from "DLL hell" that plagued Win9x. (source: WinVistaClub) This folder should not be "cleaned" through any direct process - in fact there are various protections in place to stop you from trying to do this - the only way is to uninstall any unused software (even this may leave some duplicate files around - this can't be avoided)

VPN Connection Issues in Windows Vista when using Wireless
Windows Vista uses an image-based deployment, which is HAL-independant. Use WDS to capture and deploy the images.
Managing Roaming User Data Deployment Guide - what are the Local, LocalLow and Roaming folders in Windows Vista and Windows 7 for?
Imaging Vista using StorageCraft - how to get around error message
Remove a User Profile in Vista - there is an extra step required so that you don't end up logging in with a temporary profile
File association fixes - a bunch of registry fixes to restore default Windows handling of certain file associations. This includes restoring the default ZIP file handling

Resources:

Vista includes the Remote Desktop Client version 6.

To disable the security prompt when connecting to pre-Vista computers using the Terminal Services Client in Vista change the authentication options in the advanced tab. This can also be done via a registry key, more info here.
RDP Client 6 is slow when connecting to some Windows Server 2003 machines - disable "Receive Window Auto-Tuning" which is a new feature in Vista that optimises network throughput. In an elevated command prompt type "netsh interface tcp set global autotuninglevel=disabled" - more info here.
Update for RDP on servers to stop the "using an earlier version of RDP" message when connecting from Vista

You receive an error message when you try to perform any editing tasks, or you must click to enable the compose frame in Outlook Web Access - if you get a page with a red X when composing an email in OWA, it's because the version of Internet Explorer in Vista no longer supports an Active X component that OWA relies on. Just run the update from this link on the Exchange server (note SP2 is a pre-requisite for the update).

Workaround: Download Standard User Analyzer, part of the Application Compatibility Toolkit (http://technet.microsoft.com/en-us/w.../aa905102.aspx).