Using "<Modifier>+Left/Right" to move between words in an editing window

Solution 1:

⌥ + arrow keys will let you navigate by word. As you said, ⌘ + arrow keys will move to the end/beginning of the line or document. Both of these can also be used with ⇧ to select, or the delete key. Furthermore, you can double-click to select a word and triple-click to select a paragraph — and if you double-click-drag or triple-click-drag, you can select multiple words or paragraphs.

Also useful, and perhaps familiar to you coming from Linux:

• ctrl A moves to the beginning of a paragraph
• ctrl E moves to the end of a paragraph
• fn ⌫ deletes forwards (and can be combined with ⌘ or ⌥;
  you can also use ctrlD which doesn't work with the other modifiers)
• ctrl K deletes to the end of the paragraph (kill)
• ctrl Y pastes that text back (yank)
• ctrl L scrolls so the selected text is visible
• ctrl T transposes the two characters next to the cursor
• ctrl O inserts a newline after the cursor

More interesting shortcuts and uses of the keyboard can be found here and elsewhere on the internet.

Solution 2:

• ⌥← and ⌥→ move word backward or forward
• ⌥⇧← and ⌥⇧→ move word backward or forward and modify the selection
• ⌥⌫ and ⌥⌦ delete word backward or forward

The same shortcuts with ⌃ substituted for ⌥ are used to navigate subwords in some editors like Xcode and TextMate.

A reference of the standard text editing shortcuts: hcs.harvard.edu/~jrus/Site/System%20Bindings.html

Solution 3:

Recently updated by Apple for Mac OS X 10.7 Lion:

Mac OS X Human Interface Guidelines: Appendix A: Keyboard Shortcuts

… driving me crazy … I am used to being able to use ctrl+→/← …

I highly recommend adopting the shortcuts given in the guidelines. There'll be a period of craziness whilst you learn the norms, but ultimately it'll make for a better overall experience of the operating system.

There may be user-friendly ways of re-mapping things — on a system-wide or per-application basis — but my personal experience of remapping things (years ago) is that eventually, despite best intentions, there'll be some unexpected conflict or muddle, after which you could find yourself not only choosing to learn the norms, but also extracting yourself from a muddle (making painful the deferred learning).

A good example of potential for muddle: Terminal in Lion now follows HIG (Human Interface Guidelines), which is good. You might be able to remap things for Terminal but — depending on your uses of Terminal — I imagine the risk of something going horribly wrong.