Is there a database on chemical reactions, similar to NIST, but far more complete? The only thing I'm interested in is to be able to search all reactions involving that compound in the database. Equilibrium constant, reaction rate and energy of activation would all be very welcome, but in case these data are absent it's no big deal.

Doesn't need to be an online database either, I can download a software if it contains such data.
The best known databases are Beilstein and Chemical Abstracts with around 22 millions reactions each since the end of the 19th century but they are commercial.

Organic Syntheses has made available its database for free and it covers 6000 reactions. One of the greatest advantages is that each step is described in depth and each reaction has been thoroughly tested prior to publication.

Have a look here for a list of databases.