Your online portfolio is to showcase your work and your photography skills. Creating an online portfolio is relatively easy. I've created a three step guideline for you.
1) The very first thing you need to do is organize your pictures. Go through all your shots and pick out the top 25 to 50 that you want to showcase. If you're questioning whether or not to include a picture, don't even put it into consideration. You should show your best work!
2) Edit your pictures. Don't be afraid to crop so that your subject stands out more. Do some color correction, curves, and levels adjustments. You could also bump up the color and saturation a bit.
Adobe Photoshop is your friend when it comes to editing pictures. I also suggest getting Scott Kelby's book, The Adobe Photoshop Book for Digital Photographers. This book will give you an in depth step by step guide on how the pros post process their digital pictures.
If Adobe Photoshop is too much in terms of price and learning curve, check out Adobe Photoshop Elements. It has many features similar to Photoshop, but at the fraction of the cost.
3) Display your best work online. There are numerous options you can choose from.
Put your nightclub pictures in a blog or a photoblog.
You can use a free photo sharing website.
Or you can pay a small fee and get a complete flash gallery website.
Another option is to get a domain name, web hosting, and use SimpleViewer to showcase your portfolio. This is the option that I took since I already have a domain name and web hosting. SimpleViewer is also free!
Now that you have a nightclub photography portfolio, don't forget to market yourself! Let the world know that you are a nightclub photographer through tweets, status updates on facebook, email, and blog posts.
It's also a good idea to carry around some business cards that you can give people you meet. You can get some business cards made for free at Vistaprint.