A site listing “free wallpaper collections” recently made it into the top digg-stats (actually into the ‘design category’ which is on the sidebar here as well) — so I thought I’d post a follow-up here as well. While I personally still favour InterfaceLIFT (very high resolution AND widescreen images) here’s two other sites worth browsing:
Loads and loads of categorized wallpapers, quite a good collection of seamless tiles as well, no widescreen formats, though
Another huge collection, seems to have a focus on computer generated images, hires but no widescreen formats as well
Real high-res — wallpapers spanning up to three desktops!