Here you find some screenshots of LMMS demonstrating the work with it. If you think there's an important screenshot (yours?) missing, use the LMMS Sharing Platform for uploading your screenshots!

file-browser, song-editor, project notes and Beat+Bassline Editor	plugin-browser, song-editor and Beat+Bassline-Editor	Piano-Roll (with some selected notes) and Automation-Editor
all tabs of an instrument-track-window	all plugins currently available in LMMS	3 VSTi-plugins within LMMS

Video on YouTube showing LMMS in action: