Random networks and aligned arrays of single-walled carbon nanotubes (SWNTs) can form effective thin films for flexible electronics. They can serve as either conductive or semiconducting materials in these systems, with several attractive properties, including very high carrier mobility, extreme levels of mechanical bendability and excellent optical transparency. They are compatible with low cost printing-like fabrication processes and flexible plastic substrates. Here we summarize some of our group's the latest achievements in this emerging field. In particular, we demonstrate device mobilities above 1000 cm2V-1s-1 in SWNT thin-film transistors (TFTs), with cut-off frequencies >10 GHz by use of dense, perfect arrays of nanotubes. Effective strategies to achieve high on/off ratios, in some cases >105, include electrical breakdown and selective chemical functionalization. Low operating gate voltages of ∼1 V with low hysteresis are also possible. Unusual transparent and/or stretchable TFTs based on SWNT films have been also demonstrated in some prototype devices. Complex digital circuits composed of nearly 100 SWNT TFTs and a functional nanotube radio have been successfully constructed, paving the road for nanotube flexible electronics to move from scientific research to engineering development.