Speed up

Disable unwanted and unnecessary services. Switch to a different window manager and/or desktop.
This is a common question which has many, common answers. Google: speed up ubuntu

How much RAM have you got?
There is Lubuntu or Xubuntu, you could probably add the desktop environment on your current Ubuntu and then simply change it from the login menu.

There's a new distro I recommend called Sharp OS which is built on the latest Lubuntu but has more advanced features and graphically nicer in my opinion, can also run on older machines very well with even 1gb of RAM