Since I’ve been using TiddlyWiki as my primary task manager, I move text around A LOT. Selecting, cutting, and pasting text is still much better than shuffling paper, however. Except as noted, the keyboard shortcuts below work in textarea fields of any web page and not just for TiddlyWiki. Note also that these may not always work the same way in all browsers on all platforms. I’m currently using Firefox on Windows primarily.

You may remember that one of the reasons I started using TiddlyWiki was because I wanted to be able to reorganize my list items quickly. At first I did this by selecting each item with the mouse and then cutting it using keyboard shortcuts, re-positioning the cursor with the mouse, and then pasting it with a keyboard shortcut. If you do this very much, I think you will find the following very useful. The challenge is to get them deeply ingrained in your workflow. I would suggest trying to avoid the mouse or trackpad for a week and use these as much as possible for all your text navigating, selecting, and editing. You will find the trial well worth the effort.
Cut, Copy, and Paste:
CTRL-X – Cut the selected text to the clipboard
CTRL-C – Copy the selected text to the clipboard
CTRL-V – Paste the clipboard to the current cursor position

Undo and Redo:
CTRL-Z – Undo the last editing command
CTRL-Y – Redo the last undo command

Navigating Text:
HOME: Move cursor to the beginning of the current line
END: Move the cursor to the end of the current line
CTRL-HOME: Move the cursor the very beginning of the current text field.
CTRL-END: Move the cursor to the very end of the last line of the current text field.
PAGE UP: Moves the cursor up the same number of lines as is displayed in the textarea.
PAGE DOWN: Moves the cursor down the same number of lines as is displayed in the textarea.
UP ARROW: Move the cursor up one line to the current horizontal cursor position. If the current horizontal position doesn’t exist, the cursor will move to the end of the line.
DOWN ARROW: Move the cursor down one line to the current horizontal cursor position. If the current horizontal position doesn’t exist, the cursor will move to the end of the line.
LEFT ARROW: Moves the cursor one character to the left.
RIGHT ARROW: Moves the cursor one character to the right.
CTRL RIGHT ARROW: Moves the cursor one word to the right, placing the cursor before the first letter of the next word.
CTRL LEFT ARROW: Moves the cursor one word to the left, placing the cursor before the first letter of the previous word.

Selecting Text:
SHIFT-HOME: Selects all text from the cursor to the beginning of the current line
SHIFT-END: Selects all text from the cursor to the end of the current line
SHIFT-CTRL-HOME: Selects all text from the cursor the very beginning of the current text field.
SHIFT-CTRL-END: Selects all text from the cursor to the very end of the last line of the current text field.
SHIFT-PAGE UP: Selects all text from the cursor up the same number of lines as is displayed in the textarea.
SHIFT-PAGE DOWN: Selects all text from the cursor down the same number of lines as is displayed in the textarea.
SHIFT-UP ARROW: Selects all text from the cursor up one line to the current horizontal cursor position. If the current horizontal position doesn’t exist on that line, the cursor will selects all text from the end of the line.
SHIFT-DOWN ARROW: Selects all text from the cursor down one line to the current horizontal cursor position. If the current horizontal position doesn’t exist on that line, the cursor will Selects all text to the end of the line.
SHIFT-LEFT ARROW: Selects one character to the left of the cursor.
SHIFT-RIGHT ARROW: Selects one character to the right of the cursor.
SHIFT-CTRL RIGHT ARROW: Selects all characters from the cursor to the first letter of the next word.
SHIFT-CTRL LEFT ARROW: Selects all characters from the cursor to the first letter of the previous word.

TiddlyWiki Specific:
CTRL-ENTER: Closes and accepts changes to the current tiddler being edited.
ESCAPE: Closes and discards changes to the current tiddler being edited.

If you have other useful keyboard shortcuts for manipulating text (either in TiddlyWiki or any other textarea field) that I’ve missed here, please post a comment to let me know.