The quick answer is: see video tutorials at spritetools.com

In these tutorials you will learn how to:

1) Draw and edit a vector image    http://youtu.be/rdJLS45O9XA

2) Raster images to vector images youtu.be/nPuv4jbsBgM

3) Make the first frame of a model youtu.be/vW7pkDw8VX4

4) Animate and make a sprite sheet youtu.be/R6RdZiX0EAs

5) In game testing                 http://youtu.be/NzOayKnuFbc

see section tutorials at website spritetools.com

there is video tutorials about drawing sprites in vector and about vectorizing raster sprites.

I've found it interesting.

Consider Anatomy Sprite Animator at spritetools.com

It has prepared animated models so you can just set textures or you can create your own model using 2D bone animation.

Also there are video tutorials at the website where you can learn how to draw textures, how to make a model and how to animate it.

think it's great.

Adobe Flash

Bone-based: no

Key frame concept: yes

Sprite sheet rendering: no

OS: ?

Anime Studio software is used mainly for cartoons drawing.

Bone-based: yes

Key frame concept: ?

Sprite sheet rendering: no

OS: Win, Mac

ProMotion software is used for drawing of a detailed and pixel precise graphics. cosmigo.com/promotion/index.php

Bone-based: no

Key frame concept: no

Sprite sheet rendering: no

OS: ?

GraphicsGale is a simple raster animation editor for .gif and .avi animations. humanbalance.net/gale/us

Bone-based: no

Key frame concept: no

Sprite sheet rendering: no

OS: Win

ASE (Allegro Sprite Editor) is a pixel art raster sprite editor. aseprite.org

Bone-based: no

Key frame concept: no

Sprite sheet rendering: ?

OS: ?

Anatomy is sprite animation software for 2D game development. spritetools.com

Bone-based: yes

Key frame concept: yes

Sprite sheet rendering: yes

OS: all

List of drag and drop sprite sheets creators that use another sprite sheets or frames:

Zwoptex, $15 zwopple.com/zwoptex

Predator, $15 spritesheeteditor.com

Simple sprite editor sourceforge.net/projects/simplespriteedi

list of 2D Map rendering software:

Dungeon Crafter - is a small freeware program that lets you lay down walls, floors, doors, and objects. ww2.dungeoncrafter.com

Tile Studio - Tile Studio is a complete development utility for graphics of tile-based games. tilestudio.sourceforge.net

Tiled Map Editor is another free map editor. mapeditor.org

Good luck

Consider Anatomy Sprite Animator spritetools.com

user friendly and simple enough. At the website you can find video tutorials of how to create animated character from scratch.

take a look at this website: spritetools.com

It's not a pixelart(that is good btw <img src="smileys/smiley2.gif" border="0" align="middle" />) but you can totally use this animator for your game.

Also there are a video tutorials at this website of how to create sprite animations from scratch.

good luck