Mobile Safari tweaks are plentiful in the jailbreak community, but the tweak Sleipnizer might be one of the more useful additions I've come across in the last year.
Sleipnizer isn't a flashy skin or a total reworking of the Mobile Safari interface, but adds two features that make browsing a little more touch intensive, and less invasive. The first is four new gestures that can be programmed to to perform up to 18 different actions. Users can close and open tabs, go forward and backward pages, restore tab, scroll top, and do pretty much everything except create bookmarks with touch gestures.
The second feature makes opening links a much less invasive experience. Users only need to hold their finger down on a link and it opens in the background without interrupting the user's current browsing. Finally.
The tweak is available in Cydia for $1.99 and Restore Tab buyers even get a discount.