Probably the best way of learning geography is living in another country for a while and observing how different cultures live. However as this isn't possible for most people, a good alternative is to use the Internet widely to see photographs, maps, and information about the rest of the world.
With home education, children can follow interests as they arise, learn about places that crop up in the news, or find out about countries where friends or relatives live. Below are a few geography sites which I would particularly recommend.
Water cycle - for children to discover how water evaporates and then returns to earth in a never-ending cycle. Good pictures and clear, simple text.
What is weather? - simple text and diagrams from the BBC, exploring concepts related to the weather. Suitable for children aged about 6-10.
National Geographic - link to international magazine, with many online resources, including maps, current geography-related news, and cultural information. In particular see the Kids' online magazine, which has games, interesting facts and activities for children of all ages.
Geographic.org - basic information about climates, printable maps of various types, flags of the world etc.
Dictionary of geographic terms - find the meaning of just about any geographic word or phrase in this extensive A-Z dictionary.
Oxfam: cool planet - site of the charity Oxfam, with photographs and lots of interesting information about countries it works in. Suitable for all ages.
Where learning begins: geography - American site for parents, explaining how basic geographic concepts can be learned in the early years of childhood, with plenty of information and suggestions for activities with toddlers or young children.
Kids' Ark - a site created by children for children, with links to information about ponds, folk tales, cultural information and more. The idea is to collect 'information about the world' before it all disappears.
ABC Teach outline maps - simple printable maps of each country of the world without any labels.
Owl and Mouse maps - interactive maps and puzzle games, as well as links to free games for building a town or a farm. Good for all ages, depending on interest.
NC in action: geography - for those who want to see what is covered in the UK National Curriculum, this covers topics included in schools such as economics, population change, and a few countries in detail.
Lonely Planet: destinations - click a continent or type in the name of a country, to find a basic description of facts and figures.
You might also like to see my geography page for further ideas and suggestions about introducing geography to home educated children.