command-backspace deletes a whole line. Is there a way to disable this?
Make the contents of your ~/Library/KeyBindings/DefaultKeyBinding.dict look like the text below  

/* my keybindings */

{
"@\U007F" = "deleteWordBackward:"; /* delete backwards one word */
}  



'@' represents the command key  
'\U007F' represents the delete key
'deleteWordBackward' is a keyword which Cocoa applications understand


Once you restart any Cocoa app, this will now just delete one word to the left of the cursor instead of everything between the beginning of the line and the cursor.