This is the code for the bookmarklet
Now, when I finish writing a post I click on my bookmarklet and start typing tags into the prompt. If I want to use a phrase I have to join the words together with a + like this. Phrase+Search. When I click the OK button some html code is generated and highlighted ready for me to copy/paste into the html editor of blogger. Then I publish as normal.
Yay - it works. Although not exactly categories these will do the trick.