I was trying to improve the UI on CBT and decided to develop a "hoverbutton". This is a TGraphicControl descendant that holds 3 pixmaps: Selected, Active and Inactive. Uses pixmaps for transparency. You must load the graphics at runtime using loadfromlazarusresource or some other method. It also links directly to a TPopupMenu at design time.

It's not fancy, but it works.

http://tony.maro.net/mod.php?mod=downloads&op=getfile&id=12

I've also submitted it to the downloads section on the Lazarus website.