By default GIMP comes with just a few add-ons and fat free. There is a few very easy steps to some fuel for the GIMP after clean install.
Single Window Mode:
A really great feature introduced in stable GIMP 2.80 and was available in earlier development release. Now all images gets in tabs instead of separate window. There is
some good review about it here. To enable it: From main menu select Windows -> Single Window Mode and that's all.
You can always make a your own gradients by right clicking on a selected gradient and choosing edit gradient. Here is a easiest way to make your first gradient. Select a foreground and background colors and from gradients list select FG to BG (RGB) and right
click on it. Now just simply choose Duplicate Gradient and you will have a own gradient.
Rename it by clicking on it's name.
|As you see I renamed my custom gradient to Skin.|
Another way to add more gradients in a really great pack of Web 2.0 gradient for
Scripts aka Script-fu
For Windows and MacOS you need to download a really great bundle of scripts
called FX-Foundry with such effects like cross-processing,vintage photo or soft glow. A must have scripts for editing photos.
Download GIMP FX-Foundry
For a Ubuntu like Linux open a Package Manager and look for gimp-plugin-registry . It's a pack of useful scripts and plugins for the GIMP. If you are using Mandriva,Fedora or other distribution please read the tutorial .
The Gimp always includes same brushes that I remember from version 1.8. There is hundreds of GIMP brushes available.
Gimp Paint Studio - a really great set of soft brushes and and tool presets.
Watch the features video .
1000 Free High Quality Brushes - Some links are broken.
You can also use a PhotoShop brushes via ABR plugin.
Download a Windows version from plugin registry .
Also there is a abr2gbr small command line tool for Linux and Windows for converting
Jasc Paint Shop Pro .jbr and PhotoShop .abr brushes into GIMP brushes format.
Download a Ubuntu Linux version . Search how to convert DEB to RPM if you are using
Fedora like Linux OS.
Grab some from DeviantART.com
For Linux you may find all the good plugins in Ubuntu packages repository. Just open
a Synapctic package manager and search for gimp-plugin-registry and gimp.
Here is a few plugins that I recommend you for casual use:
Save For Web - Export the images into web formats like PNG,JPEG and GIF. It allows you to selected best compression for most optimal size. Read the review.
G'MIC - Over 190 extra filters for the GIMP. From 3D to artistic like. Watch a video preview of the effects.
Liquid Rescale - A advance rescaling filter which tries to rescale image without distortion. A homepage includes a video tutorial.
Run PhotoShop plugins in GIMP - For Windows and Linux. I tried it long time and since I couldn't find any great free PhotoShop plugins I never actually use it. Want to try some PhotoShop filters? Grab a few free from here.
GAP - A GIMP animation package available for Windows and Linux. This will allow you to import movies as frames and make a nice animated GIFs.
Where to find more plugins?
http://registry.gimp.org/ a main source of plugins and scripts.
GIMP on Google+
Video Tutorials and even more on old good Youtube ;)
Official GIMP site tutorials
Have fun and don't be afraid to experiment with the GIMP.