For Tuning Guitar Online, We Recommend Tunerr.com
Tuner actually allows you to use the microphone of your computer and is very accurate. It's front facing website makes it an easy thing to just go ahead and save on your favorites bar on google chrome.
Finding The Right Tempo With Tempo Tap
Press the space bar for the beat and you can get a reading for the rhythm. Most DAWs these days may have something like this, but when you don't wanna run through the menus, it's nice to just type tempotap.com and get it done. It's a very simple site and a great tool.
HookPad For Writing Chord Progressions and Melodies
Hook theory has made some incredible progress over the last 5 or so years and is the most comprehensive and simple to understand songwriting tool that is available online. This blows my mind. You can also export MIDI files and audio files. It's free for now but may change over time (and they SHOULD charge for this). You can also see the chord progressions of other songs that have been coded with their software.
Mastering A Track Online With Mastering Box
Need a quick master? Mastering Box Is The Best We Found And It's free to use for a low quality file, and if you buy it, it's a very nominal fee compared to a mixing session with your homie. If you're the homie... charge your rate and just use this... ;)