I like that WordPress has a built in permalink builder, however I wish it had a built in way of adding your own custom rules. You can, however, write a function to hook with the flush_rewrite_rules() built in WordPress. I borrowed some of Sergey Chernyshev's .htaccess lines and created a function to add gzip compression and caching rules to speed up WordPress load time. My Google PageSpeed analysis went up about 11 points after I applied the hitaccess rules.
Achievements seem to be popping up in every new web service. Why? Because achievements make you win the Internet. Okay, not really, but it does make your user feel more engaged into your web site. It gives the user a reason to use your site and do more things on your site. The best part is the achievements do not even need to be all that difficult. Really the hardest part about implementing an achievement system into your web site is finding a good graphic designer to whip up some images.
When developing web applications it is always wise to use the most up to date APIs and know when to scale back on certain functionality. Google just posted a blog entry stating four mobile web app tips when using Google Maps. Basically it runs down to use API v3, Static API usage, StreetView Images, and JS Map usage.