PicSay is pretty awesome, and is available outside the market. I use it all the time to upload pictures to Twitter.

The main options are:
Word Balloon (many to choose from - thought, whisper, etc. As well as colouring/shape)
Title
Stickers (many to choose from)
Effects (many to choose from)
Export (to Twitter, Wordpress, Photobucket, Email etc. Depending on which apps you have installed)
Transform

Here's a picture I quickly made for this thread, with a word balloon, title, heart stickers and I somewhat pixelated the screen of my edge.

http://www.yfrog.com/5ln3zvj