The latest Groupees Build A Bundle includes the original Duke Nukem platformers, Retrovirus, Zack Zero, Oknytt and Cloudphobia amongst others. At the bare minimum, you can buy two games for $1.50 (approx. £0.94), then add subsequent games at an increasing discount. It's not the most inspiring bundle we've ever seen, though Steam trading card aficionados may be swayed by Zack Zero and Retrovirus.
Thanks to jaystan @ HUKD, both for the deal and the trading card tip!