MyPermissions.org enumerates the links to major "apps permissions" pages for sites like Google, Twitter, & Facebook. Many smaller services allow you to login with your major account & even more use feature integration, so it's important to sever access once you stop using a service. For instance, I removed Twitter access from GoPollGo, Academia.edu, Greplin, & RockMelt. I had forgotten about those last three so it was great to clear out; I might use GoPollGo in the future but presently there's no reason for it to maintain access to my Twitter.
Second comes the accounts I do not use enough to justify continuing. For most of these, what I did was scroll through 1Password, checking for accounts I have either forgotten about or do not truly need. Here are some example deletions.
high praise for Greplin at first, I rarely found use cases for it. There's definitely a place for services such as this, I just haven't found it yet. I stopped using the RockMelt browser (basically a social version of Chrome with sidebar apps) recently too & that process was analogous: a useful, interesting tool but also one with access to all my web personas.
Cloud 9 IDEOnline IDE (code editor with fancy features) with Github integration that I never got around to using. Great idea & maybe I'll return to it, but for now I don't need an account.
Other AccountsI also deleted my Campusfood, Stubhub, Meetup, Scrib, SoundClick, MySpace, PureVolume, & ReverbNation (those last four were artist profiles...I'm not still on MySpace) accounts. I deleted a Wordpress.com blog I no longer update & my account at an online retailer that I will probably never purchase from again.
I learned one major lesson from my Spring cleaning: online retaliers are the worst. Not only do they have your most sensitive (i.e. financial) information, they also are the most hesitant to empower their users. Few retailers provide a "delete account" button & many do not reply to customer support emails. All in all, it's better to centralize purchasing in online companies that get it, like Amazon, than trust a series of companies with questionable web development practices.