Is there an alternative to Adobe Fireworks?

Solution 1:

Pencil Project (Download Link)

Despite the similar names this is different from Pencil.

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The Pencil Project's unique mission is to build a free and opensource tool for making diagrams and GUI prototyping that everyone can use.

Solution 2:

Pencil (Click to install)

While mainly made for animation purpose it can be used for drawing and supports bitmap and vector graphics .

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Pencil is an animation/drawing software for Mac OS X, Windows, and Linux. It lets you create traditional hand-drawn animation (cartoon) using both bitmap and vector graphics. Pencil is free and open source.