Write Your own Bookmarklets
So you want to write your own bookmarklets? Excellent. If you haven't already done so, visit Bookmarklets.com to make sure somebody hasn't already made something similar to what you have in mind. This is also a great place to get inspiration, and it is always easier to make your own bookmarklets when you see how other people did it.
If you think your bookmarklets are good, make them available to others.
There are a few rules which you should observe to get the best results.
Also, you may want some useful tips.
Finally, as I found out myself, editing a bookmarklet by hand is rather cumbersome, as the bookmarklet must be compressed into a single line in order to execute. It is difficult to edit in this state if the bookmarklet consists of more than a few statements and you have loops, conditions, starting and ending brackets, etc. That's why I created the Bookmarklet Builder (works with Opera 7, Mozilla/Netscape 6+ and Internet Explorer).
It allows you to format the bookmarklet source code and still get the final compressed result. Furthermore, it allows you to easily test the bookmarklet - just click a hyperlink. And it has automatic syntax checking of your code. Try it out, you won't regret it.