Jazz guitar improvisation doesn't have to be scary and award-winning jazz guitarist Martin Taylor has put together a series of online video lessons on improving your guitar improvisation skills.  Martin Taylor says:

"A lot of people that play mainstream jazz are often called melodic improvisors.  This is nothing new and goes back to Bach.  In the old days they had variations on a theme.  Something that is often forgotten is that the classical composers of Europe hundreds of years ago were improvisors.   Improvisation is about being in the moment.  I use to take a melody and then play a variation on it over the same chord structure.  Each time you can move further and further away from the theme."

The jazz improvisation section includes detailed guitar tutorials on:

Improvisation Part 1: The Importance of Using Both Hands

Improvisation Part 2: Listening

Improvisation Part 3: "You're On!"

Improvisation Part 4: Flowing Ideas

Improvisation Part 5: Open Your Heart And Mind 

Improvisation Part 6 - An Example

Improvisation Part 7: Melodic Improvisation