I originaly learnt this from a tutorial off GameRenders.com, but I do it slighty diffrent so, I made a tut after Sigint asked me. :P
Ok, so today class were gonna make sig that should come out like this 'lil beauty:

So first off, make a new document, I used 320 x 110.
And fill it with the main colour of your sig, something that'll match the render.
After you've done that, make a new layer and fill that with the same colour.
Then right click layer 2 and goto Blending Options > Gradient Options and use these settings:

And your sig should look like that one in the pic.
*Before the next step this is what your sig will look like after the next step.

After that make a new layer and use your rectangular marquee tool and make a rectangle, (See pic above) then fill the inside of the rectangle with white.
After duplicate the layer and put it at the bottom of the sig.
Make another new layer and make a rectangular shape and fill it with white, then set it to soft light.
Your sig should now look like the pic above.
Now get your Custom Shape Tool out and if you havent got all of your shapes loaded, click the little arrow thing in the shape menu, goto load shapes and load the All file. I'm going to use the butterfly, now make sure that the settings at the top are the same to this:

Now press shift and drag the shape into postion on the sig.
Then one the shape layer, goto blending options > gradient options.
And use these settings:

And your sig should look like the one in the pic.
Once thats done Ctrl+Click all of the layers and press Ctrl+E the merge them all.
And then Ctrlt+Shift+U. The make them all black & white.
Ok, now get your Polygonal Lasso tool.
And your aiming to get something like this:

After the lasso bit is done fill the inside bit with the main colour of your sig.
So now we're going make the line things look like they're inside the box thing.
So get the rectangular marquee tool and trim the top and bottom on the box things.
Now its time for another shape so do what you did before but with the settings like this:

I'm gonna use Star for this one, hold shift again and put it into postion.
Once you've done that merge that line layer and the shape layer and set the opacity to about 75%.
But now we've got make the star look like it's inside the box thing, so do the same as you did with the lines. :P
You're sig should now look like this:

Now we're gonna add the render, I'm going to use an Ayumi Hamasaki one. (link:
http://img278.imageshack.us/img278/9698/ayumi21ms8yn.png )
Drag your render into your sig. (Best in the middle)
And now we're gonna make it lose a bit of colour so image > adjustments > hue & saturation. And use these settings:

Now we're going balance the colours out. So get you cutsom shape tool again and with the main colour of your sig, make a little flower or something on the top left of the butterfly.
Your sig should now look like this:

Time for text.
First type your name out. I'm gonna use One Stroke Script LET which is a default font I think. If not go to www.dafont.com and search for it.
I'm gonna have my text on an angle:

See in the box? when you see the icon thing change to a U shaped thing you can set the text on an angle.
Now I'm going put Ayumi Hamasaki text at the bottom box thing, using Times New Roman in black.
Your sig should look like this now:

Now theres just one thing left: Border.
Now I just learnt how to do a v.cool border.
So make a new document, make it 3x3 pixels. (Yep, 3x3px.)
And get the pencil tool and press D to set the colours back to black & white.
Now make a pattern like this:

Then edit > define pattern and name it something, then hit ok.
Now go back to your sig. Make a new layer, press Ctrl+A. And goto edit > stroke and make a 1px border. And once you've done then put the layers Fill to 0%.
And on the border layer goto Blending Options > Pattern Options. Click the little menu thing and select that new pattern you just made.
Make sure it looks like this:

And we're done! :)
And your sig should look like this:

Well I hope you enjoyed my tut, if you use this tut, please post your outcome, I'd love see them.
Annnd feel free post some feedback. :P
Need any help? Just post in here and I'll be glad to help. :)
Thats all from me today.... ^_^