My favorite is SoundForge by Sonic Foundry (which has recently been purchased by Sony, but it's the same development team). The full program costs $300, but they have "lite" version for only $70, called
Sound Forge Audio Studio, which has almost exactly the same feature set -- minus a few features so advanced, you'd never use them even if you did have the full version.
http://www.sonymediasoftware.com/products/soundforgefamily.aspI can't say enough about the Sonic Foundry audio and video product family. SoundForge is by far the best audio editor on the market, whether you're a rank beginner or an expert in need of highly sophisticated professional tools. We use Sonic Foundry's Vegas Video for editing all of the video projects for this website, and it's the most user-friendly and underrated video editing app on the market. It beats the pants off of Adobe Premeire and Final Cut Pro. SoundForge and Vegas have many features in common.
If you're looking for something for free, you can try downloading some shareware or freeware off of tucows (
http://www.tucows.com). Do a search for Windows software using the keyword "audio", and you'll probably find hundreds of applications. "Freeware" is completely free. "Shareware" is typically a scaled-down version of software with limited features, or a trial version. Either way, if you just want to splice two songs together this one time, almost any piece of shareware should do the trick.
Regards,
Jonathan