Interesting, do you think your logo needs updating for a reason, ie changing brand, image to push up sales, or is it you just fancy a change? Just curious what the motivation is for changing your logo, which is potentially can have a huge impact if people no longer recognise you, or mistake for a competitor.
Also, in this modern age, there is one argument that logos actually detract from online stores and with so much competition, it is better to just shout your name/web address so any browsing traffic will remember to come back, or spot you in future search results. Or have your wording as the logo.
Our logo is all that remains of the original My Local Services which I bought in 2005, albeit in different colours. We've toyed a few time with dropping it, but analysing our back link profile, lots of people use it to link to us, and it seems to be visually familiar.
Always good fun to look at some of the competition if you do a search for your industry as that can be a great pointer for ideas.

Then there is the most obvious logo in the world, Google!
To be honest logo designers aren't very expensive versus a competition, plus you can give them a brief with your ideas and they will come up with concepts. Even if you do a competition, you will still need someone to create high resolution versions for you, which a logo designer will do as part of the job.
What you could do is get a designer to come up with some concepts, and hold a competition to see which is peoples preferred one.
If you do want to do a competition style logo post, maybe shove it in the website review section.