If you are a script or plugins developer, you can upload your extensions in the Extensions Tracker, which contains

To get your script/plugin tested and then accepted in Blender you have to follow the workflow below.

[edit] You upload a script/plugin

Upload a script/plugin in the Upload Tracker (scripts, plugins) so that it has its own page.

From now on, in the script/plugin page:

[edit] If ok the script goes in Contrib tracker, and in svn!

When a script is considered useful (and safe):

it moves in the Contrib Tracker (scripts, plugins), where people can continue to discuss
most notably it is committed into bf-extensions svn under a /Contrib folder.

From now on:

up-to-date versions of your script/plugin can be retrieved checking out bf-extensions (quick howto).
(to be done yet) people checking out bf-blender svn will get your script/plugin from bf-extensions, so it will have more chances to be tested.
- A Scons option will enable the inclusion of "Contrib" scripts in ~/.blender/scripts|plugins folder.
- Another Scons option will enable Contrib plugins compiling (this is what we plan to do for Release Plugins too).

When a script is considered ready for blender release:

To checkout svn in linux, you have 2 ways.

If you intend to develop scripts or plugins, you checkout a working copy of svn:

svn checkout https://svn.blender.org/svnroot/bf-extensions

This will download the svn tree, including hidden directories ".svn" (which is used by svn to detect what you do in your working copy)

If you just mean to downlaod the scripts and plugins for using them, do:

svn export https://svn.blender.org/svnroot/bf-extensions

This will download only the tree itself without svn hidden files.

When using TortoiseSVN you can get the files by:

right clicking on the folder where you want the files to be downloaded to
then either choose SVN Checkout (if you want to dive into developing) or Export (if you only want to download the scripts and plugins for using them)
In the following window use this as the URL:

https://svn.blender.org/svnroot/bf-extensions

svn ci https://svn.blender.org/svnroot/bf-extensions

svn log

svn log -r <revision>

Example:

svn log -r 160

svn log -r <rev2>:<rev1>

Example:

svn log -r 160:149

Remember to put a message in each committ, so that a proper svn log can let other know what you've done.

Checking something in with TortoiseSVN is just as easy as downloading:

right click the file/folder you want to check in and choose SVN Commit
just don't forget to put a proper log message in your commits so everybody else knows what you were doing. Note that you can set the minimum log message length to avoid accidentally committing with an empty log message.