If you are using your blog for monetization thru different advertisement programs like Google Adsense, Yahoo Publishers Network (YPN), Chitika or direct advertisements (banner ads) then you may choose to rotate them. It is observed that the CTR (Click thru rate) of advertisement increases 
by changing the location of ads. You can try rotating advertisements on your self hosted WordPress blog by using plugins. There are lot many plugins to serve this purpose and most of them are freely available and easy to install. Here are some popular ad rotator plugins available for WordPress users.
Advertisement Rotator Plugins for WordPress
Previously it was Adsense Manager but now it is known as “Advertising Manager”. This plugin is having so many customization option and you will definitely love this plugin. Options like inserting ads in between the post is also available in this plugin. Of course, ad rotation capability is there.
[ad id=’7′ style=’float:left;margin:10px 10px 10px 0′] 2. Ad Rotator
As the name suggest, it can rotate advertisements including Google Adsense, Chitika etc. on your blog. Ad Rotator is a widget based plugin which can show HTML code from a group of code in your sidebar. This way, it rotates ads in the sidebar or wherever you want to place widget in your theme template.
This is an upgraded version of “Random / Rotate Ads” plugin. If you are using WordPress version 2.8+ for your blog, then you need to install this plugin. Yes, you can rotate ads thru this plugin as well. Google Adsense, affiliate ads, banners, images, flash, text, etc can be added and rotated thru this plugin. You just need to ad a template tag in your blog’s theme template file and then rotating ads will start appearing one by one.
4. AdRotate
Full management of advertisement programs can be done thru this plugin. You can edit and analyze performance of ads thru this plugin from dashboard only. Direct advertisement expiry and referral programs expiry notification is also available in this plugin. You can rotate between a group of ads by selecting and keeping ads in a group thru this plugin.
5. Easy Ads
“Easy Adsense” author created advertisement management tool for other publishers including Google Adsense as “Easy Ads”. Now you can use Easy Adsense to rotate and manage advertisements generated from Chitika, Clicksor, BidVertiser etc. Google Adsense code can also be put in this plugin for rotation purpose and management.
By using any of these plugins, you an rotate ads on different slots on your site. This will help you in generating more revenue thru different advertisement programs.
For 125 x 125 ad slots in your blog’s sidebar, you can use WP-125 plugin which is also having ad rotation option. Otherwise, you can have any of the above plugin to fulfill your purpose.