I recommend the IGV (http://www.broadinstitute.org/igv/home). It has a detail tutorial and supports a wide variety of data types, including array-based and next-generation sequence data, and genomic annotations. If you have installed JAVA, you can easily start from using JAVA Web Start without any install process.
Persephone Software is working on the web version of their genome browser. It is free, though does not yet have all the features of their paid enterprise desktop version. It is very fast and is tailored to show several genomes at once, linking syntenic chromosomes. Check it out at http://web.persephonesoft.com