In spite of being tempted from time to time to try out alternatives, I keep coming back to Idealist as my main tool for storing information. It is incredibly simple to use and yet surprisingly powerful. My main Idealist database currently contains about 7,000 references and 15,000 notes and yet searches are virtually instantaneous because of its full-text indexing. If the existing record types are not to your taste you can create new field and record types very easily (and you can do this on the fly in existing databases). Each database can hold up to a million records and each record can be up to 8Mb (though there is a 64K limit on the length of an individual field). Its search ability is very well thought out, enabling you to drill down quickly to precisely the records you need. In addition, simply highlighting a word or phrase in a record and pressing the Stack button will take you to a new hit list containing all the records in which that word or phrase appears. And, if you like, you can set up kinship (parent–child) relations between records. If you want to try it out, I have just discovered that it can be downloaded from here.
The owners of Idealist, Bekon, may have disappeared, but a recent flurry of comments on my earlier post gives me some faint hope that Idealist might not be dead. In particular, one of the commenters admitted to having a copy of the source code and another suggested that he might be in a position to run that source code past a developer. So perhaps it would be possible to bring Idealist into the twenty-first century (always assuming issues about ownership of the code could be sorted out).
If that were possible, I already have a wish list of things I would like to see. Top of the list would be Unicode support closely followed by RTF fields. Then, in no particular order, easy insertion of hypertext links into fields, better implementation of the kinship system, and much improved import and export.