In 1987, Villegas along with other members of the GAT compiled their poems in an anthology titled Kamao: Panitikan ng Protesta 1970-1986 that was published in the aftermath of the People Power Revolution.

[1] In 1994, in an essay titled Andres Bonifacio: Father of the Filipino Nation in a compiled publication, Tutuban: Progress and Transformation; Villegas along with fellow historians Milagros C. Guerrero and Emmanuel N. Encarnacion pushed for the recognition of Andres Bonifacio as the first President of the Philippines instead of Emilio Aguinaldo.

[6] Villegas served as the permanent curator for the BSP gold and pottery collection that was previously exhibited at the Metropolitan Museum of Manila.

Villegas served as an art advisor and helped appraise private collections held by the Ayala Corporation, the Bank of the Philippine Islands, Banco de Oro, PHINMA Property Holdings Corporation, and the United Coconut Planters Bank.

He has also worked for the Asia Society, the Asian Civilizations Museum, the Musée du quai Branly – Jacques Chirac, and other leading international institutions.

[10][11][12] Throughout his career, Villegas served as an appraiser and art advisor and cultivated a following amongst prominent Filipino collectors including Maria Theresa Virata, Richard and Sandra Lopez, interior designer Johnny Ramirez, Claude Mark Wilson amongst others.

Ocampo: From the Paulino Que Collection at the Ayala Museum that was subsequently published in an exhibition catalog authored by him.

[13] His personal collection was auctioned in 2018, consisting of Philippine colonial and modern art, ecclesiastical antiquity and ivory, Muslim craft, and jewelry.

[21] In 2019, a dining table made by artisans from Bohol from the private collection of Villegas dating from the 19th century was sold for a record PHP467,200 (US$9,470) at León Gallery auction in Makati.