Free diagramming tool for web site specification

Are there any free diagramming tools for web site specification? Which is your favourite?

From stackoverflow

• I usually use a Mind Mapping tool, here's a freebie that's very good. It's not v1 yet, but worth checking out:

  Cayra

  Download Link

  

  bob : I tried several days to download this, still broken. Any idea where I can find a mirror?

• Dia is a multipurpose diagraming tool, ala visio. http://live.gnome.org/Dia

• I'm not sure kind of diagrams you want to use but you could check out these:

  • FreeMind - an open source java-based mind mapper
  • StarUML - an open source UML tool (only for Windows unfortunately)

• Inkscape is my favourite drawing tool. Has fantastic SVG support.

• I found this one for Windows:

  • Diagram Designer

  It is basic but just what I needed to design the web structure

  @Touko, your link to StarUML is not working. This is the URL

  Touko : Thanks for noticing =)

• Just in case you're talking about sketching out the UI specifications, Balsamiq is really nice.

  JoeBloggs : The OP specifically says a) Free, which Balsamiq is not and b) web-site spec, not UI spec. I love Balsamiq, but it's clearly offtopic here.