Switching between US and Lithuanian keyboards is pain. Especially when you need to type numbers, etc.
In Ubuntu there's a keyboard layout named Lithuanian (US keyboard with Lithuanian letters). The layout works by assigning Lithuanian letters to upper row (numbers) with Alt key
These may be installed by copying them to the Keyboard Layouts folder within /Library or ~/Library; then they are enabled via the Input Sources (Input in 10.5 and earlier) tab of the Language & Text (International in 10.5 and earlier) module within System Preferences.
wget -O ~/Library/Keyboard\ Layouts/US-Lithuanian.keylayout https://raw.githubusercontent.com/evici/US-Lithuanian-Keyboard/master/US-Lithuanian.keylayout