First, let me say that I searched for this topic but could only find it as OT responses to other threads, so I thought this might be helpful for people searching for this information later.
I know some of you swear by photobucket and go through a long checklist to get your pictures posted here, but I thought I would share this easier technique.
First save the picture you want to post. Then go to tinypic.com. Click on "choose file." Then select your picture from your hard drive (leave file type and resize as they are) and click "Upload Now." You may have to enter a captcha (type a word to prove you are a real human.) Then copy the text under "IMG Code for Forums & Message Boards." You can paste that code directly into the forum thread and it is good to go. No need for a photobucket account, logging in, selecting the "tree window" above, clicking boxes, etc.
TL;DR: Go to tinypic.com, upload, use the IMG code and paste into thread. Done.