Is there any application to merge small images into a single one in a web application in order to make less HTTP request and have the page load faster?
GWT does this automatically and makes proper images + CSS styles to show those images. When I have a plain HTML + CSS is there a helper application which given HTML + CSS + a bunch of small images, outputs a proper HTML + CSS + Single Image?
See for example this Google image.
The technique you're looking for is called CSS sprites (take note of this name the next time you talk about it).
Although what you're asking for (give them your code, get back same code with sprites applied) is a little too much, some online generators do come close - they will automatically calculate the most optimal image placement and give you the CSS needed for this. Googling for CSS Sprite Generator gets back some very good ones, like http://spritegen.website-performance.org/.
You should note that these generators are not perfect, and for static sites you will need to do this ever ytime you want to tweak the graphics on the site.
