The folks over at TheAppleBlog have posted a couple of tips to make your user experience easier for those of you who have a Google Voice Account. Many folks were quite upset over the removal of GV Mobile from the App Store (BTW, ATT has more or less placed the blame at the steps of Apple), but some took solace that its still available via Cydia.
For those who still are not keen on the whole jailbreaking thing, you can still dial Google Voice and go through the prompts. Its a little cumbersome and takes time, but with this little tidbit you get the same functinality, no application to install, you have a bit of setup, but works flawlessly. The best part is, when the call is received, they will see your Google number instead of the number of your device!
To summarize the steps you basically create a new contact item for an existing contact, enter your google number, a pause and their number. Basically, this automates you having to dial your google number and follow the prompts. Check it out, they have a couple of other cool tricks in the comments.