The best SVN GUI client is Tortoise SVN. Unfortunately, it is not a viable solution on Ubuntu. KDESVN is a good alternate to Tortoise SVN.

Installing kdesvn
To install,

$ sudo apt-get install kdesvn

You might also be prompted to install Subversion, kompare and a few other libraries.

Running kdesvn
Once the installation is complete, run

$ kdesvn

on the commandline to start kdesvn.

Adding kdesvn to right-click menu
Create a file ~/.gnome2/nautilus-scripts/kdesvn.sh and add the following two lines of code:

#!/bin/sh
kdesvn $1

Assuming that your shell in located at /bin/sh. Type:

which sh

if you do not know where the shell is installed. The assign execution priviledges:

$ chmod 755 ~/.gnome2/nautilus-scripts/kdesvn.sh

In your file browser right click on any file or directory and you would see link for "open with kdesvn".

Creating a Subversion repository with kdesvn
On kdesvn, click on File > Subversion Admin > Create and open new repository. A window would open. For Path to repository, type or browse to your address. For Type of repository, choose FSFS. For details on this, see FSFS vs BDB. Check only "create main folders" option.

Checking out a Subversion repository with kdesvn
On the left window, select "trunk". The select Subversion > Repository > checkout current repository path. A window would open. Select target directory, choose revision, and uncheck "Append source url name to subfolder".