Regarding the screenshots, I find that 90% of the time I'm taking screenshots it's to show somebody something, so I really like CloudApp. (getcloudapp.com) You do the usual shift-cmd-4, but instead of copying the screenshot to the clipboard it uploads it to their service and copies a link to the clipboard. On top of that, their site is really clean.
I like Skitch.com, similar idea, but it lets you choose what you want to take a picture off, and provides a basic image editor (handy for adding annotations, highlights, etc.) before upload.
