For India, yes, for most nationalities. The Indian Government has relaxed their rules recently so that tourists from some countries can obtain visas on arrival, otherwise a visa must be obtained prior to travel. All of the Indian Embassies and High Commissions have details and downloadable application forms on their websites. Note that passports must be valid for at least six months at the time of travel.
In Nepal, visas are available on arrival. They are normally for 14 days, but can be extended to 28 days. Nepal Embassies also issue visas. It is recommended you obtain your visa prior to arrival by land.
For Bhutan, Agents in Kathmandu can arrange visas in a couple of days.
For Sri Lanka, certain nationals may visit for 30 days, obtaining a free visa on arrival.
For Tibet, our agents in Kathmandu can obtain China-Tibet visas if you are travelling from Nepal. You will need to spend a couple of days in Kathmandu while the visa is being obtained.
In all cases, it is always advisable to check with the relevant embassy.