I use photoshop a lot of people on the site didn't make their own.
most people ask in the Sig request part of the forums if someone would make
them one. As time goes on though people tend to get lazy and don't want to
make them. I make my own and help a few people. But I don't like old style sigs
and I like to have the run of the show when I make mine.
Just DL Photoshop, even the older versions are still good.
I know a few people that just use photobucket.com's photo editor.
Dead is the soul, that rots within me.
Passion is the sword, in which you used to slay it.
If you have absolutely no experience in graphics and you want to start from scratch, Photoshop is the best program to use. Gimp and Twisted Brush are both freeware and are decent alternatives, but Photoshop is the most widely used software for editing and it is much easier to learn. As for Photobucket's editor... I'll leave that simply at it doesn't work in layers like the others do and it is extremely limited.
To be completely honest, tutorials (especially the ones on YouTube) are somewhat of a waste of time in my opinion. Sure, they give you some basis as to what to do, but most of the time they are either too specific or too broad and they don't show you what you need to know.
Learning graphic design/editing can be a very long, patience-consuming process, but you learn most of it by actually doing and experimenting than listening to some random guy try to explain things and straying from the point half the time.
1. Get yourself Photoshop. CS2 is the best one in my opinion, CS3 is good as well (No opinion on CS4 yet).
2. Get yourself some simple renders and stocks (look up what those words mean if you don't know).
3. Make sure your Pictures folder (or wherever you save your stuff) is organized. This will come back to bite you if you can't find a specific image/file you want to use.
4. Have lots of patience.
5. Watch a few tutorials that teach the very basics (like what each button does and its subfunctions and such).
6. Start experimenting.
That is all the advice I can really provide.
EDIT: It's also very important to learn the terminology. If you don't know what gradient, feathering, placing (as opposed to pasting), contrast, saturation, or vignetting mean (just to name a few), you will be very lost.