Actually, you *can* do this now In the default browser, press the "Menu" button, then "More", then "Select Text". Now swipe the text you want to copy. When you release, you'll see a brief notice at the bottom of the screen saying "Text has been copied to the clipboard".

Now switch to Word/Excel, tap & hold where you want to insert, and "Paste".

To paste into the address bar, tap the address input area to get the fuller input box. Tap & hold in the input box and "Paste".