Anyone can recommend?
My favorite is Kompozer. It's derived from the original Netscape Composer.
Basically a WYSIWYG editor, though you can always hop into source mode. Simple, works OK.
Link: http://kompozer.net/
I'm not sure if they have a pricing model yet, and I haven't tested the software myself but it looks promising. Take a look at Mockingbird
Also to note, there is gliffy which does have exporting and while mostly for flowchart design, it does have some basic shapes and UI elements for page layouts. This has a free model as well as export abilities and sharing abilities.
I have a very good prototyping tool but it is not free (sorry). You can evaluate it for a month or so: Axure I'm also interested in this question. A good wireframing and prototypng tool saves you a lot of time trying to explain how things will be to your clients and to your development team!
Balsamiq is pretty nice too:
This isn't totally free, but when you use the online version you have a notice at each 5 minutes that explains how to buy, you can just click on Continue using and you can use it for as long as you want.
You can save your mockups in .xml format.
You have a lot of controls and the usage is very simple.
Someone recommended Pencil to me recently, http://www.evolus.vn/Pencil/Home.html. From the quick look I had at it it looks pretty good!