JankoAtWarpSpeed is sharing a free kit for easier sketching & wireframing of websites / web applications.

You have it all: form elements, icons, feedback messages, tooltips, navigation elements, indicators, image placeholders, embedded videos, sliders, ad banners. It is completely free for personal and commercial use.

The kit contains the  .AI, .SVG, .PDF & .EPS vector formats.

Vectordiary.com has a nice Adobe Illustrator tutorial: Drawing a Piano Keyboard.

This step by step tutorial demonstrates drawing a keyboard illustration using rectangles, grids, move and transform effects.

Access the Illustrator tutorial here.

Using Illustrator’s Live Trace function, bitmap and rasterized images can quickly and easily be converted to highly malleable vector objects. Matthew Hendershot demonstrates the Live Trace workflow, outlining all of the options available for creating traces.

Access the tutorial here.

Inkscape is an Open Source vector graphics editor, with capabilities similar to Illustrator, CorelDraw, or Xara X, using the W3C standard Scalable Vector Graphics (SVG) file format. Inkscape supports many advanced SVG features (markers, clones, alpha blending, etc.) and great care is taken in designing a streamlined interface. It is very easy to edit nodes, perform complex path operations, trace bitmaps and much more.

Download latest stable version (0.4.6) here.

Here you can find a pcak of 165 free vector icons (.ai - Adobe Illustrator files).