Steinberg released a new budget entry DAW called Sequel. Running on both Mac and PC Sequel can record, edit, mix and perform music with great-sounding loops, instruments and effects. It features a massive library of more than 5'000 loops, over 600 of ready-to-play instrument sounds, stunning effects and the same state-of-the-art audio engine that is preferred by many world-class producers all around the globe. It's only $99 and you can record, edit, mix audio and MIDI can't be bad. You can see a tutorial video HERE. One of the good things about sequel is that it all seems to happen on one window. Your mixer appears below your arrangement window. Sequel has similar functionality to the phrase sequencer in Cubase 3 where you can assign sections of your song to specific command and then sequence your song based on phrases made from sections of your song. This is useful for remixing or doing Ableton style arranging.
There are of course free alternatives. The first one is called Ardour. Ardour is a MAC only DAW. You can record, mix and edit audio. You can also use VST effects. There is no MIDI so this is just a recording solution. Ardour is free but they do ask for a small donation if you use it.
Also there is Kristal Audio Engine which is similar to Ardour except it's a PC only affair. Again it has no MIDI but you can record, edit and mix up to 16 tracks of audio with 32bit floating point audio engine. You can also use upto 3 VST insert and master effects. It has a wide range of sample rates. Krystal is free for educational and non commercial use.
Also there is Audacity. Audacity is free, open source software for recording and editing sounds. It is available for Mac OS X, Microsoft Windows, GNU/Linux, and other operating systems. Audicity is basically a multitrack audio editor like Adobe Audition without the video. It has some extremely useful features like the ability to play different tracks with different sample rates at the same time. Audacity can use VST plug-ins... infact they gave the code to Ardour. One of my favourite features in Audacity is the ability to save selection. So you can just highlight a piece of audio and save that piece without having to first make your selection a seperate audio window (like you have to in SoundForge). I find that really useful for sample editing ad loading up tunes and taking the best bits.
The last one I'll mention is Sonys' Acid Express 5. You can download ACID XPress software for free — "our free, 10-track version of ACID software. ACID XPress software will give you a taste of what ACID Pro and ACID Music Studio software have to offer. To make the music creation process especially easy, ACID XPress software has built-in Show Me How tutorials that help you step-by-step using interactive wizards and guides." Acid is very similar to Ableton so it's loop based music production.