Delhi hotels can be quite expensive for what you get, but the budget hotels can be REALLY awful. If you want to stay with all the tourists in Pahar Ganj, the only place I would stay at again is http://www.jyotimahal.net/. The rooms were mostly clean (ask for a different room if you're not happy with the first one they offer) and the rooftop restaurant has good Indian food. Try to stay closer to R.K. Ashram Marg station if you want to avoid the chaos and noise of New Delhi station.
If you want to stay in a slightly more up-market, less touristy area, try http://www.saivilla.com. It's not really budget accommodation but it's in a really good area if you want to check out fun parts of Delhi like Haus Khas Village.
I wrote this post last year, but it might be useful for your stay in Delhi: http://impossiblyindia.tumblr.com/post/35560293966/delhi-tips over 4 years ago
You can find out many hotels near IGI airport and stay and also you can try out different different hotel in Delhi for stay. You can enjoy attraction of local market and historical past of Delhi.
For more information of Delhi you can read more,
http://www.travelogyindia.com/delhi/ about 2 years ago