I think that a very good handbook, devoted to the nonlinear partial differential equations, is: A. D. Polyanin and V. F. Zaitsev, Handbook of Nonlinear Partial Differential Equations, Chapman & Hall/CRC Press, Boca Raton–London, 2004 (first edition) and 2012 (second edition). Another very good handbook on nonlinear PDE's, is: Lokenath Debnath, Nonlinear Partial Differential Equations for Scientists and Engineers, 2012 (I have given here a lin to Springer website with this book online).
There is also a handbook by Zwillinger, and for nonlinear first-order PDEs there is also a classic book by Kamke in German, see the links below the text.
Also, to complement the answer of prof. Stepien, Zaitsev et al. have an online handbook giving solutions to a number of nonlinear PDEs at
http://eqworld.ipmnet.ru/ ; in particular, see
http://eqworld.ipmnet.ru/en/solutions/npde.htm.
Finally, an important class of PDEs possessing infinite families of exact solutions, are integrable systems (see e.g. https://en.wikipedia.org/wiki/Integrable_system for details). For these, see the online Encyclopedia of integrable systems at http://home.itp.ac.ru/~adler/E/e.pdf
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