This is a powerful, free cross-platform audio editor (works with both PC and MAC). You’ll have to install it on your computer, but then will be able to make an audio file with multiple tracks. Click here for a pretty wide-ranging manual for working with this software.
Here are two video tutorials for using Audacity:
Freesound is a collaborative database for free, Creative Commons-licensed audio. You’ll need to create an account to download files, but then you’re free to import and integrate them into your project.
An interactive library of free music, which you can download and import/integrate into your project.
Soundcloud is a free service for hosing audio files… it can accept AIFF, WAVE, FLAC, OGG, MP2, MP3, AAC, AMR and WMA files types. After you upload the clip, Soundcloud will process them into its own elegant HTML5 player. You will have to create an account at Soundcloud, but then can upload your audio there before embedding your project into the blog.
If you have specific questions, post them below and we’ll try to answer them as quickly as we can.