Usability 
A self described "App Store for the 3 Billion Users Who Don't Have an iPhone", GetJar is the largest and one of the oldest (since 2004) off-portal download sites for free java and native mobile games and applications. Getjar's catalog contains 10,000 plus titles and the site delivers over 16 million downloads per month worldwide. And according to MocoNews, GetJar recently started working with carriers to provide the GetJar experience on-deck as well. Getjar has already signed up 10 carriers including 3 UK.
There's a full web version (Getjar.com) with a searchable and browasable directory of games and applications. Listings can be filtered to exclude apps not compatible with your device. Listings include a screenshot, description and user reviews and ratings. Files can be downloaded to your PC for side loading. Or you can make note of a five digit "download code" that can be entered on the mobile site for a direct to mobile download.
The mobile version of the site has a mobile formatted version of the same searchable, categorized directory of apps and individual pages for each app with descriptions and ratings but no screenshots.
Downloads are free, the applications and games are mostly freeware or ad supported but some are trials and demos. The type of each download (free full version, free ad-supported or trial/demo) is clearly indicated in each listing.