Much of the money I make across my sites is from paid to post articles. In the past I have reviewed three of the four sites/services that I use. (See Payperpost review, Sponsored Reviews and Smorty reviews.)

After another month or so of using these services, let's re-review the pros and cons of each.

Payperpost
Actually the best by far in terms of professionalism, support responsiveness and even variety of posts available. The problem with Payperpost is simply too many bloggers chasing too few opportunities. You have to 'reserve' opportunities in the pool (only the ones that your blog qualifies for too). Even remaining on the site all day and refreshing periodically, I have managed to reserve just one posting opportunity in a month. Although this is annoying and doesn't result in much revenue, I will stick with the program simply because of their professionalism and helpfulness.

Smorty
Smorty allocated you opportunities. That means you log on periodically and see what opportunities are awaiting you. Although this means you get to write posts it also means that you have no choice - you accept the assignment or you don't. They chose the post and the blog to post too. On the other hand, they pay promptly and the site has improved recently in terms of information and ease of use.

Sponsored Reviews
another site and yet another system. Here, you bid on opportunities. They seems to add several opportunities a day so there is generally something to bid on. That would be great except that few opportunity providers bother to respond either way so you site with a huge list of opportunities that you have bid on waiting for someone to approve or decline. Old opportunities do expire but I'd rather see a rejection than expiry.

The other thing about Sponsored Reviews is that you name your own price (within bounds) - this cuts both ways because if you ask too much then I guess you get rejected - but beware - you only get 60% of what you actually bid.

Regular payers and no problems interacting with the site.

Blog to Profit
This is the fourth service I have used and it is not as good as the others but occasionally throws up an opportunity. It works by you defining criteria for your blog and then they assign writing opportunities based on those criteria. The issue is that the criteria are very broad and frankly not relevant to my sites so I get lots of assignments that just don't fit my site topics so I don't accept them.

They have just improved the site layout and functionality and it is a big improvement. Again though, they allocate the opportunity and name the price - generally $5. So not very flexible.

On the other hand they pay promptly too.

Overall

Overall, Payperpost and Smorty are my favorites. It would be Payperpost if I could just get a few more assignments. Sponsored Reviews is a close second but I dislike the lack of feedback from the opportunity posters there.

Good luck with your paid posting!