I used a plug in to retrieve all the post from a category. The post is displayed in an unordered list
<ul><li> and everything if fine, even the
<a> tags to the post.
Now, for more usefulness (it's a word?), I would like, on hover of the link, to display the first image of the nextgen gallery found in this post. I do not have enough know-how to retro engineer the ngg plugin, but there should be a way to get, let's say the thumbnail of a post and set it as a tooltip.