Deutschland

Georg Forster, the naturalist on Cook's second voyage, along with the Resolution, is shown on a stamp issued by the DDR in 1979. In 1988, the DDR issued a stamp showing the DDR Antarctic Research Base, which was named after Forster.

DDR	20/03/1979	Famous Scientist 1v This 35p stamp shows Georg Forster and the Resolution.
DDR	22/03/1988	Antarctic Expedition 1v This 35p stamp shows the Georg Forster DDR Antarctic Station.

España

Byron's Voyage

The Dolphin and Tamar passed the island of Palma in the Canaries on the outward leg of their voyage (21/07/1764).

Wallis's and Carteret's Voyages

The Dolphin and Swallow passed the island of Palma together with the Prince Frederick on 16/09/1766.

Cook's Early Survey Work

Cook stopped at Tenerife in the Canary Islands on his very first transatlantic voyage to Canada on the Pembroke in 1757.

Cook's Third Voyage

He also stopped in Tenerife on the outward leg of the third voyage, 1 August 1776.

I am not aware of these explorers ever sailing to mainland Spain. Spain issued a set in 1967 called Builders of the New World which includes two stamps (50c & 3p) that feature maps based on Cook's travels along the Pacific coast of North America.

España

12/10/1967

Builders of the New World Two of the stamps in this set show maps based on Cook's maps. The 50c value shows Nootka, and the 3p shows the coast of Alaska and Canada.

Portugal - Açores

Wallis's Voyage

The Dolphin passed Cape Pico and Fyal on 24/04/1768, before heading home for Britain.

Carteret's Voyage

The Swallow sailed between St. Michael and Tercera on the 07/03/1769, before heading for England.

Cook's Second Voyage

Cook stopped here on the homeward leg of his second voyage, 14 July 1775.

I don't think Açores or Portugal have issued any stamps with any mention of Cook.

Portugal - Madeira

Byron's Voyage

The Dolphin and Tamar spent a week in Funchiale Bay, Madeira in July 1764 on the outward leg of their voyage.

Wallis's and Carteret's Voyages

The Dolphin, Swallow and Prince Frederick stopped at Madeira (07-12/09/1766).

Cook's First Voyage

Madeira was Cook's first port of call during his first Pacific voyage, 12 September 1768.

Cook's Second Voyage

He also called here on the outward leg of the second voyage, 29 July 1772.

I don't think Madeira or Portugal have issued any stamps related to these voyages.

Sverige

Anders Sparrman, who joined the second voyage at Cape Town, was shown on a Swedish stamp issued in 1973. Daniel Solander has just recently been shown on a joint issue with Australia.

Sverige	22/09/1973	Swedish Explorers 5x1v This booklet of five 5k stamps includes one that shows Anders Sparrman and a Pacific Island.
Sverige	16/08/2001	Daniel Solander (Joint Issue with Australia) 2v The lower value stamp shows a portrait of Solander and a drawing of Barringtonia calyptrata. The higher value shows a drawing of Cochlospermum gilliraei and a picture of the Endeavour caught on the Great Barrier Reef.