Microsoft Excel is really a wonderful tool. It can be used for all kinds of things and I have found it extremely useful to use as an Information Professional.
For example, I have used it to keep track of all the subscriptions we have, including having a spreadsheet dedicated to subscriptions, users and costs and have a separate spreadsheet dedicated to descriptions of the subscriptions and what category it belongs to.
I have also used it to organise what I would like our SharePoint site to look like, having a separate tab for each page on the site, which makes it easier to update as we would just need to copy and paste, since SharePoint can be limited in what it can do.
In addition, I have used Excel to keep track of important information, which has, in a way, become a guide. For example, I have used it to record the different searches we perform (including what database to use and what to look for), who our suppliers and account managers are and the different company registries.
Most importantly, it is being used to keep track of our requests so that we have an idea of who is asking for what, what kind of information they are asking for and how long each type of request takes.
I find Excel useful because it allows me to have a number of sheets in one document and I can filter, alphabetise, calculate and update information really quickly and easily.