Custom URL shortener

Hey guys, the URLs on my site are somewhat long (not a huge problem) but I would like some kind of plugin that can shorten URLs with a custom domain service..so rather than using a popular one like bitly or something, I wanna have my own auto service so when I post something on my WordPress, it creates a short URL, either on the same domain im hosted on or on another one of my shorter domains… so I have a nice short URL for sharing at the end of the day…any ideas where I can start?