I think the most similar and closest competitor is the Savant Genome Browser. Like IGV, it is a stand-alone, java-based application which allows you to quickly upload and visualize NGS data (e.g. bam files) in the context of a reference genome, annotation tracks, custom bed files etc. It has a number of different visualizations and plugins which distinguish it from IGV. But, in general they are quite similar. If you've used IGV then Savant will be fairly intuitive and the choice between them is somewhat subjective. My impression is that development of Savant is maybe a little bit more open and community-driven than IGV. The Savant paper from summer 2012 gives a good overview. Which Multiscale Genome Browser Is The Best At Visualizing Structural Variants? compares Savant and IGV in the context of visualizing structural variants.
I used to use IGB (http://bioviz.org/igb/) for visualising things like bed files. I think it's pretty. I switched to IGV since I started working mainly with NGS data though, as it's the one everyone recommended. Haven't tested whether and how well IGB can deal with it. Uploading custom tracks to UCSC also actually works pretty nicely, particularly since it gives you so much other data you can visualise alongside your own.
Finnish super computing center CSC is developing a qutie powerful one, "Chipster Genome Browser", available here (you can webstart it from the link on the page). It is also written in Java, just like IGV.
I usually use artemis for visualizing NGS data. Artemis is a free genome browser and annotation tool that allows visualisation of sequence features, next generation data and the results of analyses within the context of the sequence, and also its six-frame translation. http://www.sanger.ac.uk/resources/software/artemis/