A client of mine had several sites and had created a simple spreadsheet in excel for this. There were 4 different pages I think, Account, Blog, Social Networking ... and then there was something else, sorry I can't remember... Anyway it went something like this;
The accounts page had the cpanel info, passwords, login, email set up details, and persona name. The blog page had all the sites with blog info login on them. WP pw, database info etc. The social networking page had all sites like twitter, stumble upon etc with persona name login and passwords etc.
Hope that gives you some idea of what can be done. Good luck.
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