My favorite Clipboard Manager ArsClip (just a 860 KB exe) offers an extra hotkey for pasting as plain text.

Example configuration:
CTRL + V = Paste (normal)
WIN + V = Paste as plain text

Some other features:

• Multiple permanent items groups
• Picture, RichText, File Copy, Unicode, HTML support
• Keypress emulation
• Form Mode for pasting multiple fields
• Highly configurable

Download:
http://www.joejoesoft.com/vcms/97/

There's also AceText -- which is the one I use the most -- it's a good balance of

When a thought hits your mind, write it down in AceText. When you come across useful information on a web site or in a document, copy and paste or drag and drop it into AceText. Never again forget a good idea or lose a scrap of paper with valuable notes.

Use AceText's full-featured text editor to take notes and write down ideas at any time. Quickly jot down a brief thought, or hold a long brainstorming session writing down, organizing and sorting out ideas. Easily store web site addresses, text snippets or even whole documents. Drag and drop or paste them directly into an AceText collection. Move or copy previously captured text from the clipboard history and other AceText collections.

    What is ClipMagic ?
   
    ClipMagic is a powerful Clipboard Extender and Information
    Manager for storing Images and Text, either automatically or
    manually in a categorised format, with details of the URL if the
    text is from an Internet site.
   
    To save something simply copy it to the Windows Clipboard by
    pressing CTRL-C or right click on the mouse and select Copy.
    ClipMagic then automatically stores it and if you have set up
    Rules & Filters the clip will be moved into a particular
    category.
   
    Clips can easily be retrieved either by copying from ClipMagic
    and pasting into your application or by using HotKeys or using
    the new PastePicker.