I made a timeline for some animation software I'm writing.
http://atlas.walagata.com/w/peterbone/Pivot.zip (no source)

The timeline is not like flash because it actually displays the frames as small images for easier navigation. I used TImages inside a TScrollBox. This makes it easy for frames to be inserted or deleted because you just change the positions of the images when 1 is deleted/inserted instead of having to redraw them all. I use the OnClick event of the TImage to select a frame - each TImage has it's tag value set the the frame number so it can tell which image was clicked.
Maybe you don't want this kind of timeline, but I thought I'd mention it anyway.

Peter