Derek,
First off, there is the free option of using the NWS radar. Some feeds can be a bit slow, but hey, it's free! There are several other sites that provide free radar images. Be sure to pay attention to the times on radar images!
Weathertap is another alternative. It isn't nearly the quality of GRLevel3, but it has a lot of good features. It's a browser based interface, not a separate appliction like GRLevel. (there may be an app that you download, but I've only seen it used through a browser). For something like $7 per month, you can get access to radar, along with various other pieces of information. However, with GRLevel3 being a one time $80 fee, the bang for your buck is better saving up and buying the GRLevel software.
Scott