Useful Magento Modules Free and Paid

Free:

Blog: http://www.magentocommerce.com/magento-connect/blog-community-edition.html

Google Trusted Store: http://www.magentocommerce.com/magento-connect/google-trusted-stores.html

Ebay/Amazon Integration: http://www.magentocommerce.com/magento-connect/ebay-magento-integration-order-importing-and-stock-level-synchronization.html

Google Shopping Integration: http://www.magentocommerce.com/magento-connect/google-content-api-for-shopping.html

System Configuration Search: http://www.magentocommerce.com/magento-connect/system-configuration-search.html

Multi-Table Rates: http://www.magentocommerce.com/magento-connect/site-management/shipping/webshopapps-matrixrate-1-multiple-table-rates-extension-certified-bug-free.htmlbased on weight, price, quantity

Admin Order Gride Customizer: http://www.magentocommerce.com/magento-connect/enhanced-admin-grids-editor.html

Mail Chimp Integration: http://www.magentocommerce.com/magento-connect/marketing/email-marketing/mage-monkey-mailchimp-integration-4865.html our recommended solution for your email marketing

Product Tabs: http://www.magentocommerce.com/magento-connect/magento-easytabs.html allows more advanced configuration for product info page

Allow Deleting Orders: http://www.magentocommerce.com/magento-connect/asperience-deleteorders.html

SMTP Email Settings: http://www.magentocommerce.com/magento-connect/aschroder-com-smtp-pro-email-free-and-easy-magento-emailing-for-smtp-gmail-or-google-apps-email.html

Paid:

RMA $149: http://ecommerce.aheadworks.com/magento-extensions/user-experience/rma.html

Points & Rewards $299: http://ecommerce.aheadworks.com/magento-extensions/featured/points-and-rewards.html has some very nice features like awarding points for reviews, referrals, purchases

Gift Cards $130: http://www.magentocommerce.com/magento-connect/gift-cards.html

Live Chat (Zopim) $11.20/month http://www.magentocommerce.com/magento-connect/zopim-live-chat.html

Facebook/Twitter/Google+ discounts for likes/tweets/+ $90: http://amasty.com/facebook-twitter-promo.html

Special Occasions coupons $79: http://amasty.com/special-occasion-coupons.html

Extra Checkout Fields $119: http://www.aitoc.com/en/magentomods_checkoutfieldsmanager.html

Extra Address Fields $79: http://amasty.com/address-attributes.html

Menu Editor: $65: http://store.paradoxlabs.com/easy-menus-for-magento.html or $59 Flexible Menus: http://amasty.com/flexible-menu.html

Multi-Fees $149: http://www.mageworx.com/multi-fees-magento-extension.html

Development Toolbar $49 Commerce Bug 2: http://store.pulsestorm.net/products/commerce-bug-2

CRM ZenDesk Integration $39.99 + Zendesk Monthly Fee: http://turbobird.net/pricing-versions

Email Forms $89: http://mageme.com/magento-extensions/webforms-professional-edition.html

PDF Related

PDF Customizer Fooman PDF makes it easier to edit and customize your order, invoice, and other PDFs $61.50: http://store.fooman.co.nz/magento-extension-pdf-customiser.html

Order QR Code Generator Moogento Pickpack $89 allows generating a pick sheet PDF with QR codes for each product: http://www.moogento.com/magento-pickpack-picklist.html

One Page Checkout

Aheadworks $89: http://ecommerce.aheadworks.com/magento-extensions/one-click-checkout.html

Apptha $99: http://www.apptha.com/category/extension/Magento/OneStepCheckout#ratings_review

Magestore $149: http://www.magestore.com/magento-one-step-checkout-extension.html

Aitoc $129: http://www.aitoc.com/en/magentomods_one_page_checkout_booster.html#reviews

Webtex $139.95: http://www.webtexsoftware.com/step-by-step-one-page-checkout-magento-extension

Shipping Labels

UPS Labels $149: http://www.infomodus.com/magento-extensions.html

FedEx Labels $179.99: http://www.cobbconsulting.net/magento-fedex-extension.html

Shipping Manager (Auto Generate & Pay For Shipping Labels For Various Carriers)

Shipworks ($15 - $50/month Depends on Volume): http://www.shipworks.com/shipworks/

Ship Station ($25 - $145/month Depends on Volume): http://www.shipstation.com/features/

SEO

SEO Suite Pro $149: http://www.mageworx.com/seo-suite-pro-magento-extension.html

SEO Suite Ultimate $399: http://www.mageworx.com/seo-suite-ultimate-magento-extension.html

Aheadworks SEO $149: http://ecommerce.aheadworks.com/magento-extensions/ultimate-seo-suite.html

Affiliate Programs

$99 Magestore: http://www.magestore.com/affiliateplus/pricing.html/

$99 Aheadworks: http://ecommerce.aheadworks.com/magento-extensions/magento-affiliate.html

Quickbooks Integration Options

T-hub atandra order manager with quickbooks export $300: http://www.magentocommerce.com/magento-connect/t-hub-for-quickbooks.html

Cartspan $500 http://www.cartspan.com/Frontpage/

eBridge starts at $1000: http://www.ebridgeconnections.com/blueprint/

Traxian depends on volume: http://www.traxian.com/account/buynow/magento.html

Magnetic One Store Manager $499 + Quickbooks $129: http://www.magentocommerce.com/magento-connect/store-manager-for-magento.html & http://www.magentocommerce.com/magento-connect/quickbooks-integration-addon-for-store-manager-8305.html

Netfira $99/month: http://www.netfira.com.au/Products/magento.aspx