Avalon is a 140 processor Alpha/Linux Beowulf cluster constructed entirely from commodity personal computer technology and freely available software. Computational Physics simulations performed on Avalon resulted in the award of a 1998 Gordon Bell price/performance prize for significant achievement in parallel processing. Avalon ranked as the 113th fastest computer in the world on the November 1998 TOP500 list, obtaining a result of 47.8 Gigaflops on the parallel Linpack benchmark. Avalon currently provides over 15,000 node-hours of production computing time per week, split among about 10 production users. Obtaining an equivalent amount of computing through Los Alamos institutional sources would cost a minimum of $45,000 per week. The machine also supports code development for another 50 users. The largest single simulation was performed in April and May 1998 using the SPaSM molecular dynamics code, which computed a total of 1.12 x 1016 floating point operations. This simulation is among the few scientific simulations to have ever involved more than 10 Petaflops of computation. The price of hardware and final assembly labor for Avalon totalled $313,000 dollars. The monetary cost of the development and OS software used for the applications mentioned above was $0. Perhaps most extraordinary, all of the hardware and software maintenance on the machine is performed in the spare time of four people, averaging less than 10 man-hours of labor per week overall.