Copernic Desktop Search: Vista's Search is fast and smart and so is Copernic's, with keyword, file content, Boolean and wildcard searches. If you don't like the look and feel of copernic. Google Desktop makes a good substitute.
Desktop Sidebar: Vista has a handy windows Sidebar with calendars,calculators, a quick link to your media player and RSS feeds. Desktop Sidebar offers similar features, with zillion of add-ons including a file browser, a weather summary, news updates and an e-mail checker. Too complicated for you? Then try the simple LaunchBar Commander. which lets you create a multiple on-screen panels for launching various applications and documents.
Vista Start Menu SE: This utility creates a fair limitation of Vista's Start menu, but adds functions that Vista lacks, built-in shortcut keys to frequently used windows functions as Reboot, Switch Users, and Hibernate. Another great alternative for organizing apps and files is JetStart FREE; it's faster than Vista Start Menu SE, but less fancy.
Visual Task Tips: This clever tool pops up a preview, a miniature image of the open window in the taskbar. Scroll you mouse wheel up or down the image to resize it.
Folder Marker: Customize your folder icons and icon backgrounds with Vista icons. Folder Marker is a snap to use, and you can visit Horizon Software to download a bunch of Vista icons.
WindowBlinds 5: One prominent Vista feature you might like is Windows Glass, the semitransparent colored edges that Windows Aero has. WindowBlinds 5 provides skins, visual styles and themes that allow you to change the look and feel of many parts of Windows XP. Its not a FREE software(though you can get the crack), lets you midify toolbar icons, the Start Menu and Start button as well. Get the Vista Plus Version 2 skin at the WinCustomize site.