Symphonies and string quartets are typically for Haydns works. Sonatas and piano-trios also made Haydn famous.
Also famous are Haydn's musical jokes. For example a sudden loud chord in the "Sinfonie mit dem Paukenschlag" ("symphony with the beat of the drum") to wake sleeping listeners. Or the pretended ends in the quartets op. 33 NR. 2 and op. 50 NR. 3.
Haydn wrote 104 (!) symphonies and 24 operas. Further 83 string quartets, fairs, oratorios and piano works (like sonatas).
Haydns orchestras, excluded the Londoner time, were smaller than those later classical musicians and sounded thinner. This goes along with the musical tradition at that time. After Johann Sebastian the composers were on the search for musical styles and they experimented. Haydn's employers, above all Esterhazy, had a certain budget available and that was limited to a relatively small orchestra. With Morzin this consisted of 16 men, with Esterhazy of 25 men.
Sure there are annual musical celebrations in honours of the composer, since 1986 "Haydn Festspiele Eisenstadt" (Haydn festival in Eisenstadt / Burgenland / Austria) and there within the "Haydntage" ("Haydn-days"), where works by Joseph Hadyn are performed. But the focus always is set on the complete works of the composer.